The United Nations said Friday that it had successfully transferred more than one million barrels of oil from a dilapidated Yemeni tanker, removing the imminent risk of a spill. 

UN Secretary General Antonio Guterres "welcomes the news that the ship-to-ship transfer of oil from the FSO Safer to the Yemen replacement vessel has been safely concluded today, avoiding what could have been a monumental environmental and humanitarian catastrophe," a statement said.

The milestone means that "the core aspect" of a years-long effort to address the threat posed by the Safer, often referred to as a "ticking time bomb", is now finished, said UN Development Programme head Achim Steiner. 

"That removes the imminent and immediate threat that had become the focus of attention across the whole world: a tanker that could break apart or explode in the Red Sea," Steiner told AFP.

The next phase of the project, stripping and cleaning the Safer's tanks and preparing it for towing and scrapping, is expected to take "anywhere between two to three weeks", Steiner said.