Houthi rebels have turned a medical centre in Yemen’s contested city of Hodeidah into a sniper position, a sign the Iran-backed group is “militarising” hospitals, and using civilians as human shields, Amnesty International has warned.

The report came as more than a dozen aid groups sounded the alarm about the “catastrophic” impact of renewed fighting between the rebels and a Saudi Arabia-led coalition over the Red Sea city.

Just a day before, the United Nations warned that dozens of starving children being treated at Hodeidah’s largest hospital, Al-Thawra, were at “imminent risk of death” because the building was just metres from the front line.

Meanwhile, a Save the Children-supported clinic in another part of town was hit by gunfire on the same day, destroying a pharmacy that held lifesaving medicines.

Amnesty said Houthi gunmen in a pickup truck forced staff out of a hospital in Hodeidah’s 22 May district on Friday and placed a team of snipers on the roof, turning it into a potential target for air strikes, in violation of international law.

“This is a stomach-churning development that could have devastating consequences for the hospital’s medical workers and dozens of civilian patients, including many children being treated there,” said Samah Hadid, Amnesty International’s Middle East director of campaigns.

“Placing gunmen on a hospital roof blurs lines which should never be blurred. Hospitals are not a target: the sick and injured have an absolute right to safe medical treatment at all times, and medical workers must be allowed to carry out their lifesaving work,” Ms Hadid added.

Placing gunmen on a hospital roof blurs lines which should never be blurred. Hospitals are not a target Samah Hadid, Amnesty International

Hodeidah has become the latest and arguably most fierce battleground between the Iran-backed Houthi rebels and a Saudi Arabia-led coalition who have been fighting over the country for three and a half years. The ruinous war has ripped apart Yemen, which is now on the brink of famine and in the grips by the world’s largest humanitarian crisis, in terms of numbers.

The UN has warned that 13 million people could die from starvation if the fighting continues; around 23 million, meanwhile, rely on outside aid to survive.

Fighting first erupted in the spring of 2015 when Saudi Arabia and its Gulf allies, including the UAE, launched a bombing campaign to reinstate Yemen’s recognised president Abedrabbo Mansour Hadi, who had been ousted by the Houthis when they swept control of the country months earlier.

Nearly four years later, there is little hope of an end to the conflict.

Over 30 local and international charities released a joint statement on Thursday calling for an immediate ceasefire. A separate statement signed by 14 charities, including Save The Children and Care International, warned that civilians were being used as human shields in Hodeidah as the fighting has intensified over the last few days.

More than 150 people have been killed as the Gulf coalition has pounded the Houthi rebels with coalition artillery, helicopter gunships and airstrikes in an apparent rush to take the strategic city before the end of a US-set deadline to enforce a ceasefire.

At the end of last month, the Trump administration called on all sides to agree to a truce within “the next 30 days”, in order to reboot the peace process that collapsed in September.

Despite the massive increase in violence, Saudi coalition officials claimed in interviews with The Independent they had not launched a full offensive but were merely setting up “defensive positions”. They added that the coalition was fully committed to peace talks should the Houthis participate and agree to relinquish their weapons.

Children suffering from acute malnutrition in Yemen Show all 17 1 /17 Children suffering from acute malnutrition in Yemen Children suffering from acute malnutrition in Yemen Doctors take some blood of Yemeni Yousef Abdullah Bakhit Ali, 13, suffering from severe acute malnutrition. With ongoing and unending conflict in Yemen, humanitarian situation continues to deteriorate across the country Unicef/Huwais Children suffering from acute malnutrition in Yemen A doctor weighs Yemeni baby Yahya Hamoud Ali Al Huzef, 9 months suffering from malnutrition Unicef/Huwais Children suffering from acute malnutrition in Yemen Ali Mohammed Ahmed Jamal,12 years old and suffering from severe acute malnutrition. He arrives with his family at a Unicef supported treatment centre in a hospital in Sanaa Unicef/Huwais Children suffering from acute malnutrition in Yemen A doctor measures the arm of Yemeni Ali Mohammed Ahmed Jamal, 12, who is suffering from malnutrition at a treatment centre in a hospital in Sanaa Unicef/Huwais Children suffering from acute malnutrition in Yemen There are over 400,000 severely malnourished children in need urgent lifesaving assistance in Yemen Unicef/Abdulhaleem Children suffering from acute malnutrition in Yemen Ali Mohammed Ahmed Jamal is weighed Unicef/Huwais Children suffering from acute malnutrition in Yemen A doctor measures the arm of baby Yahya Hamoud Ali Al Huzef Unicef/Huwais Children suffering from acute malnutrition in Yemen Unicef are currently working to reach 275,000 malnourished children with critical life-saving supplies and care for over 5 million people with safe and clean water to stop the spread of life-threatening diseases Unicef/Huwais Children suffering from acute malnutrition in Yemen Yahya Hamoud Ali Al Huzef with his family in his house in the outskirts of the capital Sanaa Unicef/Huwais Children suffering from acute malnutrition in Yemen The country is on the brink of famine and children's chances of survival are becoming slimmer by the day Unicef/Abdulhaleem Children suffering from acute malnutrition in Yemen Ali Mohammed Ahmed Jamal has his arm measured Unicef/Huwais Children suffering from acute malnutrition in Yemen Unicef are currently working to provide nearly 1 million children with vaccines and healthcare Unicef/Huwais Children suffering from acute malnutrition in Yemen Doctors take some blood of Yemeni Yousef Abdullah Bakhit Ali, 13 years old suffering from severe acute malnutrition at a treatment centre in a hospital in the capital Sanaa on November 2, 2018. (Release obtained) With ongoing and unending conflict in Yemen, humanitarian situation continues to deteriorate across the country. There are over 400,000 severely malnourished children in need urgent lifesaving assistance in Yemen. The country is on the brink of famine and childrenâ€™s chances of survival are becoming slimmer by the day. UNICEF are working with partners around-the clock to save children suffering from malnutrition and disease. We are currently working to reach: â€¢ 275,000 malnourished children with critical life-saving supplies and care â€¢ Over 5 million people with safe and clean water to stop the spread of life-threatening diseases â€¢ Nearly 1 million children with vaccines and healthcare â€¢ 9 million people with emergency cash assistance to help families buy basic commodities so they can survive Â© UNICEF/UN0253367/ Huwais Unicef/Huwais Children suffering from acute malnutrition in Yemen Unicef are working with partners around-the clock to save children suffering from malnutrition and disease Unicef/Abdulhaleem Children suffering from acute malnutrition in Yemen Unicef are currently working to provide 9 million people with emergency cash assistance to help families buy basic commodities so they can survive Unicef/Huwais Children suffering from acute malnutrition in Yemen Ali Mohammed Ahmed Jamal is suffering from malnutrition Unicef Children suffering from acute malnutrition in Yemen On 31 October 2018 in Yemen, the Al Thawra Hospital in Hodeidah where children are being treated for severe acute malnutrition. UNICEF Regional Director for Middle East and North Africa Geert Cappelaere visited Yemen from 29 October through 1 November 2018. As of 30 October 2018, over 11 million children â€“ 80 per cent of all children in the country â€“ require humanitarian assistance, due to the impact of the ongoing conflict. Worsening years of underdevelopment, attacks against civilians and civilian infrastructure and lack of salary payments for most civil servants have pushed basic services for children to the brink. Children face food shortages, disease, displacement and an acute lack of access to basic social services. One out of three children in Yemen is at risk of acute malnutrition. Â© UNICEF/UN0253574/Abdulhaleem Unicef/Abdulhaleem

However, the Houthi rebel’s chief Abdulmalik al-Houthi vowed on Wednesday never to surrender, even if they were outnumbered.

“Does the enemy think that penetrating this or that area, or seizing this or that area, means we will be convinced that we should surrender and hand over control?” the rebel leader said in a televised address.

“This is not happening and will not happen ever,” he added.

In Thursday’s joint charity statement, the rights groups warned that civilians were now trapped in Hodeidah.

“Most routes out ... are now blocked by fighting, severely impeding humanitarian agencies’ ability to transport aid and supplies to those in need across Yemen, and preventing residents from fleeing to safety,” the statement read.

On the same day, the International Committee of the Red Cross said that the upcoming peace talks cannot be “an excuse to disregard the laws of war”.