Saudi-backed forces have begun an assault on the key port of Hudaydah after Houthi rebels ignored a final deadline to withdraw, reports say.
Rebel positions are being bombarded from the air and sea, according to BBC quoting regional media.
Aid agencies have warned of a humanitarian catastrophe if the city is attacked, with up to a quarter of a million casualties possible.
The port is the main entry point for humanitarian aid into Yemen.
More than seven million people in the war-torn country are dependent on food aid.
The Saudi-owned Al-Arabiya network reported that the “liberation” of Hudaydah had begun with a large-scale ground assault supported by air and naval cover.
Explosions were heard on the outskirts of the port city, it added.
The Yemeni government of President Abdrabbuh Mansour Hadi said in a statement that all political means to persuade the rebels to withdraw had been exhausted.
The United Arab Emirates (UAE), part of the Saudi-led coalition that backs Mr Hadi, had earlier given the Houthis a final ultimatum to withdraw or face imminent attack.
UAE Junior Foreign Minister Anwar Gargash told the BBC that the coalition had run out of patience with diplomatic efforts after a previous 48-hour deadline expired.
He said the coalition wanted the UN to take control of the port but it was prepared to take military action if the Houthis refused to withdraw.
The civil war in Yemen has killed about 10,000 people over the past three years and created what the UN says is the world’s worst humanitarian disaster.
- Trump-Kim summit: Pentagon remains ‘ironclad’ after war games cancelled
The Pentagon has reassured allies of its “ironclad” security commitments, after President Donald Trump cancelled its Korean military exercises.
Mr. Trump made the announcement after Tuesday’s historic summit with North Korean leader Kim Jong-un in Singapore.
The move is seen as a big concession to North Korea and appeared to take US allies in the region by surprise.
Meanwhile, North Korean state media said Mr. Kim had accepted an offer from President Trump to visit the US.
The BBC quoted KCNA news agency saying Mr. Kim had invited Mr. Trump to visit Pyongyang “at a convenient time” and Mr. Trump had also invited Mr. Kim to the United States.
“The two top leaders gladly accepted each other’s invitation,” reports added.
In his first reported comments since the talks, Mr. Kim said it was “urgent” to halt “irritating and hostile military actions against each other.”
He said the two countries “should commit themselves to refraining from antagonising” each other “and take legal and institutional steps to guarantee it.”
The Kim-Trump summit was the first such meeting between the two countries – centred on nuclear disarmament and reducing regional tensions.
It concluded with a one-page agreement.
In the press conference afterwards, however, Mr. Trump added another announcement: the cancellation of the military exercises.
The drills, often called “war games,” are held in South Korea with local forces and US soldiers stationed there.
Mr. Trump also said he wanted to bring US troops home – although he did not specify a time frame.
He said the drills were “provocative” – even though the US has previously defended them – and there were suggestions that US allies had not been forewarned of the move.
South Korea’s Presidential Blue House said it needed “to find out the precise meaning or intentions” of Mr. Trump’s statement.
South Korean President Moon Jae-in spoke by phone with Mr. Trump for 20 minutes late on Tuesday, but an official readout of the call made no mention of military exercises, according to Reuters.
- Stranded migrants: Macron scolds Italy over Aquarius ship
French President Emmanuel Macron has accused the Italian government of “cynicism and irresponsibility” for refusing to let a stranded rescue ship packed with migrants dock in Italy.
Meanwhile the 629 migrants have sailed off to Valencia, Spain aboard two Italian ships.
Spain is some three days’ sailing away.
Italian Prime Minister Giuseppe Conte hit back angrily at France, calling its stance on migrants “hypocritical.”
He criticised “countries that have always preferred to turn their backs when it comes to immigration.”
In the past five years Italy has taken in more than 640,000 mainly African migrants and says its EU partners must ease the burden.
Most migrants who survive the perilous voyages from North Africa end up in overcrowded Italian camps. Among them are refugees fleeing war and persecution, who have a right to asylum.
The Aquarius migrants, mainly sub-Saharan Africans, were picked up off Libya’s coast at the weekend.
They were found in inflatable boats and are now being looked after by Doctors without Borders (MSF) and the Franco-German charity SOS Méditerranée aboard the Aquarius.
Mr. Macron’s spokesman, Benjamin Griveaux, said the French president recalled that “in cases of distress, those with the nearest coastline had a responsibility to respond.”
“There is a degree of cynicism and irresponsibility in the Italian government’s behaviour,” he quoted President Macron as saying.
- Florida man kills four children and himself after police standoff
A man in the US state of Florida fatally shot four children before turning the gun on himself after a 21-hour standoff, police say.
Police found Gary Wayne Lindsey Jr, 35, dead in the apartment where he had held the children – aged one to 12 – hostage in Orlando.
Lindsey was the father of two of the children.
He was a felon on probation for arson among other charges.
His girlfriend had called police after he battered her during an argument.
A family lawyer identified the four children killed: Iraya, 12; Lillia, 10; Aidan, six; and Dove, one.
At a news conference on Monday, reported by CNN, Orlando Police Chief John Mina called it “a very tragic and sad ending.”
Chief Mina said it was not clear when the children were killed.
Swat officers entered the apartment on Monday night.
They “found that all four children had been killed by the suspect by apparent gunshot wounds and it appears the suspect took his own life as well,” Chief Mina said.
“Our hearts go out to all the families involved.”
Police said at least one child was dead when officers attempted to give Lindsey a phone to communicate with police negotiators.
An officer who had been injured in the initial confrontation with Lindsey, Kevin Valencia, remains in a critical condition, the police chief said.
According to court records, Lindsey had been arrested several times over 15 years.
- Renowned chef, José Andrés feeds thousands in Guatemala after volcano eruption
Armed with tamales and a whole team of volunteers, renowned chef, José Andrés, travelled to Guatemala four days after the eruption of Fuego volcano, to feed the masses.
Andrés is most popular for his small delicate tapas, but throughout the years, the small plates have turned into big missions.
In Guatemala, Andrés and his team of 12 volunteers, have been preparing a total of 6,000 meals a day to feed those who have been affected by the volcano eruption.
The eruption claimed more than 90 lives, thousands were displaced, and even though there are shelters, many are run by volunteers and don’t have a feeding operation.
With the help of local government, private sectors, and other non-governmental organisations, Andrés, along with his nonprofit, planned an effective feeding plan to deliver meals to 18 distribution points.
Andrés founded the non-profit World Central Kitchen after the devastating earthquake in Haiti in 2010.
The mission was simple – to make food an agent of change.
After Hurricane Maria hit Puerto Rico, Andrés and his team served over 3.4 million meals since they arrived in September.
They continue to help the island.
The team also sent out volunteers during the California wildfires and to Hawaii after the Kilauea volcano eruption.
Earlier this year he partnered with various DC restaurants to put together Food For Our Lives, a collaboration that offered free and discounted food to students who marched in DC on March 24.