Amnesty International says intense fighting near Yemen’s largest port of Hudaydah has displaced tens of thousands of people, warning against the spread of clashes to urban areas.

The rights group said on Thursday that “the worst could be yet to come” after surveying civilians who made the perilous escape from front line towns south of Hudaydah port.

Saudi-backed militants are advancing towards the western province, which is under the control of Yemen’s popular Houthi Ansarullah movement.

“The human impact of this fresh military offensive on Yemen’s western coastal areas is clear from the distressing stories shared by civilians displaced by the conflict,” Rawya Rageh, senior crisis response adviser at Amnesty International, said in a statement.

Citing a report by the United Nations, the rights group said clashes along Yemen’s western coast have displaced around 100,000 people in recent months, most of them from Hudaydah Province.

“It is a glimpse of what potentially lies in store on a wider scale if the fighting encroaches on the densely populated port city” it added.

Amnesty said fleeing the fighting has been costly for those who could actually afford it.

The vast majority of the displaced said “they could only fund the trip by selling precious belongings, such as wedding rings, property deeds and livestock.”

“They left on private buses and trucks, paying an average of 10,000 riyals (around £22 per person, a large amount in the local economy). In some cases, large families paid up to 150,000 riyals to escape,” it said.

One woman from Qataba said she fled during fierce clashes, and while she managed to bring her infant and toddler daughters, she left behind her mother and seven-year-old son.

“We left not thinking we would survive. We thought we would surely die… [but] by the end of it we hoped we died instead of going through what we went through,” she said.

Saudi Arabia and its allies launched the war on Yemen in March 2015 in support of Hadi, a close ally of Riyadh. The Yemeni Ministry of Human Rights announced in a statement on March 25 that the Saudi-led war had left 600,000 civilians dead and injured until then.

The Saudi-led countries have also blockaded the already-impoverished Yemen, causing widespread famine and food insecurity.

According to United Nations figures, a record 22.2 million people in Yemen are in need of food aid, including 8.4 million threatened by severe hunger.