Syria has extended permission for the United Nations to use two additional border crossings for post-earthquake aid for three more months, a Syrian official said on Saturday.

Syria "has decided to extend the permission it granted to the U.N. and its specialised agencies to use the two border crossings of Bab Alsalama and al-Ra'i for an additional period of three months ending on 13 August," Bassam Sabbagh, Syria's U.N. ambassador, said in a tweet.

"This decision is based on Syria's keenness on enhancing stability and improving the living and humanitarian situation of all Syrians, and comes within its efforts to facilitate the delivery of humanitarian aid to all those in need in all Syria," he added.

Syrian President Bashar al-Assad initially agreed to open the two crossings for three months starting on Feb. 13, a week after an earthquake that killed more than 50,000 people in Turkey and Syria. Parts of the northwest are held by groups opposed to Assad in the 12 year-long civil war.

The U.N. on Friday asked Syria's government to extend its approval for the two crossings to deliver aid into opposition-held zones, a spokesperson said.

(Reporting by Maya Gebeily Editing by Jason Neely and Mark Potter)