The Iran-backed Houthis seized control of Yemen's entire Red Sea coast and captured three strategic islands on Friday, in a lightning offensive that cemented their hold on a vital shipping corridor linking Europe and Asia.

The developments are likely to deepen the Middle East war's impact on international commerce, as Saudi Arabia shut down an oil pipeline following attacks, and after months of Iran's blockade of the Strait of Hormuz.

Following a week-long offensive that has left hundreds dead, government officials said the Houthis seized the Yemeni side of the Bab al-Mandab Strait, the southern gateway to the Red Sea and the Suez Canal.

A local official with Yemen's Saudi-backed government said on Friday that the Houthis had "completed their takeover of the Bab al-Mandab area and Mayyun Island".

A government military official later reported the group had also seized Greater and Lesser Hanish, the last two islands in the narrow waterway not under their control, as well as all of the neighbouring Red Sea coastline.

"Everything that was under our control on the western coast has fallen," the military official added.

A witness told AFP that gunmen were "deploying along the Bab al-Mandab shore and are driving around in military vehicles".

The capture of the islands, particularly Mayyun in the middle of the strait, heightens the Houthis' ability to attack Saudi tankers, which they have been targeting since July.

Saudi Arabia, the world's biggest oil exporter, has relied on the Red Sea ever since Iran's Hormuz blockade choked off its shipments via the Gulf.

Mohammad Mokhber, an adviser to Iranian supreme leader Mojtaba Khamenei, congratulated the Houthis on their "resounding victory" on Friday.

Farea Al-Muslimi, research fellow at Chatham House, told AFP: "Now the Iranians don't only control... the Strait of Hormuz, but they control the other most strategic chokepoint in the Middle East."

Oil prices have soared past $100 a barrel this week, while average US diesel prices topped $6 for the first time on Friday -- a potential headache for President Donald Trump ahead of midterm elections.

The Houthis' military spokesman, Yahya Saree, said navigation through the Bab al-Mandab Strait was "safe" for all but Saudi Arabia following the latest advances.

'Great victories'

The Houthi offensive has killed more than 500 people, according to sources on both sides.

It has also displaced about 46,000 people, the UN migration agency said on Friday.

It is part of renewed hostilities in Yemen's civil war that began with the group's takeover of the capital Sanaa in 2014.

Houthi supporter Abdulhamid Dhaifallah lauded the group's "great victories" in and along the strait.

"They have been preparing for this front for four years," the Sanaa resident said.

Satellite images from Copernicus Sentinel Data taken on Thursday showed black smoke billowing near Medina, along the general route of the East-West pipeline that carries Saudi oil to its Red Sea coast.

The Saudi energy ministry on Friday announced that attacks led to the closure of the pipeline -- which it had been increasingly using to bypass Hormuz -- adding that injuries were recorded.

"The East-West pipeline in the Riyadh and Medina regions was subjected to several attacks on Thursday morning," a ministry official told the SPA news agency, adding: "The pipeline was stopped as a precaution, and the attacks resulted in some injuries."

Before the Red Sea offensive, the Houthis already controlled a large part of Yemen's north.

They have recently attacked government-held areas in Hodeida and Taiz provinces and swept down the coast, seizing the port city of Mocha and Zuqar Island, north of Bab al-Mandab, on Thursday. 

Mohamed, 46, who fled Mocha in the middle of the night, told AFP there was an "apocalyptic" atmosphere in the historic city.

Dangerous conflict

On Friday, the spokesman for the Yemeni government forces, Majed Abdullah Al-Nazili, said they had begun shelling areas along the Taiz-Mocha road, while residents told AFP they heard airstrikes. 

While Saudi Arabia has also hit back with airstrikes and ordered troop reinforcements from Aden, where the internationally recognised government is based, it has failed to stop the Houthis' advance.

Houthi media said two Saudi strikes hit Mocha's airport on Friday, while a local official said the city's seaport was hit by six missiles of unknown origin.

"I think the Saudis have tried everything they can to avoid this war, but I don't think they have any more choice," said Al-Muslimi. 

The ongoing exchanges risk reviving a war that killed hundreds of thousands of Yemenis and sparked one of the world's worst humanitarian crises.

The Houthis, after seizing Sanaa and forcing out the government, fought a Saudi-led coalition from 2015 until a UN-brokered ceasefire in 2022.