The Saudi-led military coalition carried out a series of airstrikes across Yemen Friday, killing dozens and striking an ambulance for a hospital supported by the international medical charity Doctors Without Borders, according Yemeni officials, rebel media and a statement by the charity.

The intense wave of airstrikes came as the Qatari-based Al-Jazeera network said three of its journalists had been kidnapped in southern Yemen.

The charity, also known by its French acronym MSF, said the ambulance driver was killed in an airstrike on the northern town of Dahyan on Thursday. Dahyan is part of Saada province, the stronghold of Shiite rebels who control much of the country including the capital, Sanaa. The rebels, known as Houthis, announced that airstrikes in Dahyan killed 26 people.

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In Sanaa, officials said that 22 people were killed in strikes that targeted the mountain of Nahdeen believed to house weapon caches. In Dhamar, Taiz, and Jawf, similar airstrikes targeted gatherings of Houthis and allied army units. In the port city of Hodeida, at least 10 civilians were killed when airstrikes targeted trucks carrying smuggled oil from the port, according to officials.

The officials all spoke on condition of anonymity because they were not authorized to speak to the press.

Yemen's civil war began when the Houthi rebels, allied with a former Yemeni president, overran the capital in September 2014. In March 2015, a coalition of countries led by Saudi Arabia began airstrikes and later, a ground operation to retake the country. More than 5,800 people have been killed and over 80 per cent of Yemen's population is in dire need of food, water and other aid, according to the United Nations.

Meanwhile, three Al-Jazeera journalists working in the war-ravaged city of Taiz who went missing this week were most likely kidnapped, the satellite news network said.

Reporter Hamdi al-Bokari and crew members Abdulaziz al-Sabri and Moneer al-Sabai were last seen Monday night in Taiz, a city in southern Yemen that has been the scene of heavy fighting for months now, the Qatari broadcaster said.

The network said it was "in contact with related parties in Taiz" to find the men and ensure their safety.

In a statement late Thursday night, Al-Jazeera's acting Director-General Mostefa Souag called for the men's immediate release.

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"Our colleagues were simply doing their job of reporting the story and informing the world on what is taking place in Yemen," Souag said. "It is tragic to see that in times of conflict, news organizations continue to be targeted. Journalists should have the freedom to do their work without the fear of intimidation, abduction or unlawful arrest."

The network said al-Bokari, a Yemeni national, has worked for Al-Jazeera's Arabic channel since 2006. Al-Sabri is also a reporter for Al-Masdar newspaper, while al-Sabai works as a driver, according to the New York-based Committee to Protect Journalists.

Taiz, Yemen's third-largest city prior to the war, sits in the country's rugged interior mountains. It is of strategic importance because it lies along a main route from the port city of Aden, which Saudi-led forces hold, leading to rebel-held Sanaa.

For months, residents and aid groups say the Houthis have been indiscriminately shelling Taiz and blocking the delivery of humanitarian aid there.

Journalists also have been targeted in the conflict. Houthis have detained reporters while at least four journalists have been killed in airstrikes by the Saudi-led coalition, according to CPJ.

On Sunday, 35-year-old reporter Almigdad Mohammed Ali Mojalli, who contributed to the Voice of America, Britain's Daily Telegraph newspaper and the Nairobi-based Integrated Regional Information Networks, was killed in an apparent Saudi-led airstrike outside of Sanaa.

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"Security in Yemen has rapidly deteriorated in the past year, making it one of the most dangerous places in the world to work as a journalist," Sherif Mansour of CPJ said in a statement Thursday night. "We call on all parties to cease targeting journalists and to free immediately all members of the media that they are holding."