The regime of Syrian President Bashar al-Assad has begun moving chemical agents in the country’s arsenal to the port city of Tartus.

According to diplomatic sources quoted in an interview published in the Kuwaiti Al-Rai newspaper, the regime is attempting to create a “safe zone” for top leaders and their families. It is not clear, however, which chemical agents, or what amount, were moved.

According to the reports, Syria is believed to possess “several tons” of chemical weapons-grade material, including sarin gas. They are stored in some 20 separate sites around Syria, according to a report published Thursday in The Washington Post.

American and Middle East official sources told the newspaper there might also be other sites of which they were unaware, adding that various intelligence agencies were monitoring the situation.

The arsenal had been developed with assistance from Russia and North Korea for use against Israel, they added.

U.S. President Barack Obama and numerous other Western officials warned Assad against using Syria’s chemical weapons several months ago – and after hearing reports of the move, made similar calls to Assad again on Saturday.