A leak has been reported from the crumbling tanker moored off Yemen's west coast, which is carrying more than 1.1 million barrels of oil, a top Yemeni official said on Monday.
The oil tanker FSO Safer has been rusting away since 2015 and is likely to wreak havoc if it sinks or explodes in the Red Sea.
For months, the UN has attempted to send a team to assess the risk amid international calls for action, but efforts to unload the oil and make the rusting hulk safe have been hampered by Iran-backed Houthi rebels.
“Urgent and important. There is a leakage from the oil pipeline in the Safer tanker. A disaster will happen in the Red Sea if urgent action is not taken,” Waleed Al Qudaimi, the Hodeidah deputy governor, wrote on Twitter.
“The failure of the UN Security Council to implement its decisions on the tanker has simply shown that it's not a priority,” Mr Al Qudaimi said.
The Yemeni official called on states bordering the Red Sea, such as Saudi Arabia and Egypt, to take urgent measures to prevent an environmental disaster.
Last month, Yemen's Foreign Minister Ahmed Awad bin Mubarak said rebels were “holding the oil tanker hostage and are refusing to allow the UN to inspect it".
The Houthis' refusal will “cause a real catastrophe that will destroy Yemen and the region’s marine environment. Its effects will extend to the world,” Mr Mubarak said.
Negotiations between the UN and Houthi rebels in control of the area where the ship is moored failed earlier this year.
The tanker was used as bulk storage to export the country's small crude oil resources but has been lying unsecured for years.
Last year, the government said the tanker must be disposed of immediately and warned of an environmental catastrophe if it breaks apart.
It has had almost no maintenance since the conflict in Yemen intensified in 2015.
If the oil spills, it could have devastating consequences for the Arab world’s poorest country, which is already dealing with a civil war and a severe humanitarian crisis.
The UN has warned repeatedly of the risk of a spill four times the volume of the 1989 Exxon Valdez disaster in Alaska in which more than 10.8 million gallons (37,000 tonnes) of oil was lost.
In November, the Houthis approved the UN mission, but later changed their minds.
The UN wants engineers to inspect the vessel, carry out light repairs and return later for a more comprehensive job. But the Houthis want all repairs completed during the first visit.
The UN declined to comment when contacted by The National.