The Saudi-led coalition has allowed 4 fuel ships to dock at Yemen’s Red Sea port of Hodeidah, two sources familiar with the matter reported, after the Houthi group announced it would only agree to a ceasefire proposal if an air and sea blockade were lifted.

Four vessels, including two carrying a total of 45,000 tonnes of gas oil, a ship loaded with 5,000 tonnes of liquefied petroleum gas and a fourth tanker with 22,700 tonnes of fuel oil have received clearance from the coalition, the sources added.

As of Wednesday morning, the 4 vessels had not yet started moving towards Hodeidah port, which is controlled by the Iran-aligned Houthi group battling the Saudi-led coalition in Yemen.

Nasser Sharif, the deputy transport minister of Yemen’s Saudi-backed government, wrote on Twitter that a number of oil ships had been allowed to the port of Hodeidah to ease the humanitarian situation. He did not elaborate.

Mohammed Abdulsalam, the Houthi chief negotiator, said: “The provision of fuel, food, medical and basic goods is a humanitarian and legal right for the Yemeni people. We do not accept any military or political conditions for receiving them.”

The blockade of Yemeni ports has been one of the major causes of the world’s worst humanitarian disaster.

United Nations data showed that coalition warships off Hodeidah were holding up 14 fuel tankers as of March 23 even though they had secured U.N clearance. Some have been waiting six months to dock.

Four other ships left without docking after waiting months.

Saudi Arabia, which leads a coalition that has been fighting the Houthis since 2015, offered the group on Monday a ceasefire deal which would also include reopening Sanaa airport and allow fuel and food imports through Hodeidah port.

The Houthis said the Saudi offer fell short of their demand for a complete lifting of the air and sea blockade, but that the group would continue to talk to the Kingdom, the United States and mediator Oman in pursuit of a peace deal.

On Tuesday, the Houthis launched a drone attack on an airport in southern Saudi Arabia.