Yemeni forces have pushed back a large-scale assault by militants and mercenaries on the port city of Hudaydah, a source in the so-called Saudi coalition has told Agence France-Presse.

Saudi Arabia and the United Arab Emirates have deployed about 10,000 new troops to Yemen's west coast after repeated campaigns to seize Hudaydah were thwarted by Houthis and their allies in the Yemeni army.

After 11 days of clashes, Saudi-backed militants say they have now reached residential neighborhoods in Hudaydah's east, sparking fears of street fights that would further endanger civilians trapped in the city.

Medics and military sources were quoted as saying Monday that nearly 150 people had been killed in 24 hours of clashes, including several civilians.

Based on a tally provided by AFP, 110 protectors of the city and 32 invaders were killed overnight. A military official in Hudaydah confirmed seven civilians deaths, without giving further details.

Houthi fighters and their allies, however, have pushed back the massive offensive to occupy Hudaydah, the news agency admitted, citing a source in the coalition as saying.

Residents told AFP that Yemeni snipers had taken positions on rooftops in eastern Hudaydah, a few miles from the port on the western edge of the city, in preparation for street battles.

Battle-hardened Houthi fighters and their allies are expected to fare better in street battles. To overwhelm them, Saudi Arabia and the UAE are most likely to resort to heavy bombing of the city in order to pave the way for ground advances.

This Reuters photo shows a view of the Red Sea port city of Hudaydah, Yemen, June 14, 2018.

On Monday, UN Secretary General Antonio Guterres warned that the destruction of the vital Yemeni port of Hudaydah could trigger a "catastrophic" situation.

"If the port at Hudaydah is destroyed, that could create an absolutely catastrophic situation," Guterres told France Info radio during a trip to Paris.

The massive invasion has put the safety of nearly 600,000 people living in Hudaydah at risk and imperiled the livelihoods of millions of others dependent on the port for shipment of scarce food and humanitarian aid into Yemen.

Yemen is under a Saudi blockade which has put the impoverished nation on the brink of the worst humanitarian crisis in 100 years, according to the United Nations.

In their offensive against Hudaydah, Saudi Arabia and the UAE are using heavy weapons and armaments, enlisting many mercenaries from Africa and elsewhere amid close aerial support by military helicopters and fighter jets.

Mariam Aldogani, Save the Children's field coordinator in Yemen, has said the people in Hudaydah are living in a "state of fear."

The intensified battle for Hudaydah comes despite Pentagon chief James Mattis calling last month for a ceasefire and negotiations between Yemen's warring parties within 30 days.

Both the United States and Britain are major suppliers of arms to Saudi Arabia. British Foreign Secretary Jeremy Hunt was due in Saudi Arabia on Monday, with the Foreign Office saying he would press King Salman and Prince Mohammed to support UN efforts to end the conflict.

Head of Yemen's Supreme Revolutionary Committee Mohammed Ali al-Houthi said in an op-ed published by The Washington Post on Friday that the escalating offensive in Hudaydah showed Mattis' ceasefire call was "nothing but empty talk."

Saudi Arabia launched its devastating military campaign against Yemen in March 2015. According to the Armed Conflict Location and Event Data Project (ACLED), the war has claimed the lives of around 56,000 Yemenis so far.

On Friday, a senior Houthi official said Yemen would turn into a "graveyard” for aggressors as Saudi-backed militants announced that they had begun a military operation to take over Hudaydah.