WASHINGTON

The US urged its nationals Friday to "immediately" leave Syria, citing escalating fighting between rebels and regime forces that have intensified the "volatile" security situation.

"The security situation continues to be volatile and unpredictable with active clashes between armed groups throughout the country," the State Department said in a security alert for US citizens. "The Department urges U.S. citizens to depart Syria now while commercial options remain available."

It added that Americans who choose not to leave or are unable to should prepare "contingency plans" for emergency situations and be prepared to shelter in place for extended periods.

The civil war in Syria has intensified in recent days, with anti-regime groups, led by Hay’at Tahrir al-Sham, fighting regime forces since Nov. 27 and making significant advances.

Anti-regime forces captured much of central Aleppo on Nov. 30, following a rapid push from its western countryside.

In their latest offensive Thursday, the groups seized the center of Hama, solidifying control of the city and forcing regime forces to retreat.