DUBAI (AFP) - Air strikes and fierce clashes shook the outskirts of Yemen's rebel-held port city of Hodeida overnight, pro-government sources and residents said on Sunday (Dec 16), despite a United Nations-brokered ceasefire.

At least 29 fighters, including 22 Houthi rebels, were killed on Saturday night in clashes and air strikes in Hodeida province, a pro-government military source told AFP.

He added that seven rebels were captured during an attack on Al-Durayhimi district, which lies about 20km south of Hodeida city.

A resident of the city reached by telephone said that the clashes were "fierce" and the sounds of jets could be heard throughout the night until about 5am local time on Sunday.

The fighting comes days after a UN-backed ceasefire came into effect, part of a hard-won accord agreed in Sweden between Yemen's warring sides.

The truce between Yemeni government forces, backed by a Saudi-led military coalition, and the Houthi rebels was due to be followed by the withdrawal within days of fighters on both sides.

In comments published on Saturday on the rebel-run Saba news agency, the Houthis accused pro-government forces of shelling residential neighbourhoods in Hodeida city.

Last Thursday's ceasefire accord had been seen as the most significant step towards ending the devastating conflict in Yemen, where more than 14 million people are on the brink of famine.

A prisoner swap involving some 15,000 detainees is planned and a "mutual understanding" has been struck to facilitate aid deliveries to Yemen's third city Taiz - under control of loyalists but besieged by rebels.

The two sides also agreed to meet again in late January for more talks to define the framework for negotiations on a comprehensive peace settlement.

The UN says the conflict has killed some 10,000 people and unleashed the world's worst humanitarian crisis.

Human rights groups say the death toll could be five times as high.