Saudi airstrikes and fierce clashes have shaken the outskirts of Yemen's Hudaydah despite a UN-brokered ceasefire that Yemenis already feared could collapse at any moment.

Residents were hoping that the ceasefire reached in Sweden Thursday would provide them a respite after months of clashes which have seen a push by Saudi Arabia and the United Arab Emirates to seize Hudaydah thwarted.

But heavy clashes broke out on the outskirts of Hudaydah overnight following fresh attempts by Saudi and Emirati troops and their mercenaries to advance into the city amid aerial bombings.

A military source loyal to Yemen's former Saudi-backed regime told AFP that least 29 fighters, including 22 Houthis, had been killed on Saturday night.

He also claimed that seven Houthi fighters had been taken captive during an attack by pro-Saudi militants in Hudaydah Province's Durayhimi district.

A Hudaydah resident said the fresh fighting was "fierce" and that the sounds of fighter jets, operated by Saudi Arabia and its allies, could be heard throughout the night until Sunday morning.

Yemen's army spokesman Brigadier Yahya Sare'e said on Saturday that dozens of Saudi air raids had targeted residential neighborhoods across the impoverished country and dropped cluster bombs on citizens' farms in Hudaydah.

In a statement carried by Yemen's official Saba news agency, Sare'e said Saudi mercenaries, supported by heavy shelling of artillery and rockets, had tried to infiltrate into Durayhimi from several directions.

"They tried to sneak into the positions of our forces but the army and Popular Committees responded, killing and wounding a number of them," he added.

Later in the day, the coalition's jet fighters also launched new airstrikes on the Yemeni town of Bayda, leaving three people, including two children, killed.

The clashes came after Yemen’s Houthi movement and the former Saudi-allied regime agreed Thursday to cease fighting and withdraw their forces from Hudaydah following week-long peace talks in Sweden.

UN Secretary General Antonio Guterres said the ceasefire agreement would see "a mutual redeployment of forces from the port and the city," with the UN playing "a leading role" there to facilitate humanitarian access.

The truce was the first significant breakthrough in Yemen's peace process, which is aimed at ending the Saudi war that has killed tens of thousands of people and pushed the country to the brink of famine.

What are these children guilty of?

Why all these crimes against childhood?

A child was critically injured by the US proxies Saudi/UAE Aggression air raids in Hodeida province Al-Tuhayta area #Yemen 09-12-2018#HumanRightsDay#اليوم_العالمي_لحقوق_الانسان

pic.twitter.com/MU74slWeb9 — مازن هبه (@MazinHebah) December 10, 2018

However, Houthi chief negotiator Mohammed Abdulsalam said on Friday there was no sign that the Saudis were "going to stop their aggression against the innocent people of Yemen despite the ceasefire deal."

Abdulsalam called on the Yemenis to remain vigilant, especially in Hudaydah and Tai'zz, and continue supporting the Yemeni army and popular committees.

'Ceasefire date set for Tuesday'

On Sunday, a spokesperson for the Houthi leadership said the UN had set the Hudaydah ceasefire date for December 18.

"The Houthis received a message from the UN, setting the date to begin the ceasefire between the warring parties in the city of Hudaydah on December 18," he told Doha-based Al Jazeera broadcaster.

A Woman killed, others civilans injured, in #Saudi-led coalition's bombardment on #Hodeida. Saudi led coalition has carried out more than 18000 air raids since March 26, 2015, with weddings, medical facilities and funerals not spared from the bombardment. Dec.11#Yemen#Anonymous pic.twitter.com/OfxfwL1k5v — News2Tor (@News2Tor) December 11, 2018

The chairman of the Supreme Revolutionary Committee of Yemen, Mohammed Ali al-Houthi, said he hoped that the opposite side would observe the Hudaydah truce.

“We hope that the US-Saudi-UAE coalition and its allies in Yemen will commit to the date of the ceasefire in the field, as a beginning of ending the aggression,” he tweeted on Saturday.

Hudaydah, a lifeline for millions of Yemeni people, is the entry point for most of the country’s commercial goods and vital aid. The port has seen some of the heaviest fighting in the four-year Saudi war on Yemen.

Saudi Arabia and the UAE launched their offensive against Hudaydah in June but they have faced a strong resistance put up by Yemeni armed forces – led by the Houthis -- as well as the city’s residents.