WASHINGTON: The State Department on Friday ordered nonessential American diplomats and the families of staffers at the US Embassy in Beirut to leave Lebanon immediately due to security concerns as the Obama administration and Congress debate military strikes on neighboring Syria.

The department also authorised the voluntary departure of diplomats and families at the US Consulate in Adana, Turkey, which is the closest American diplomatic post to Syria in Turkey.

In a new travel warning for Lebanon, the department said it had instructed nonessential staffers to leave Beirut and urged private American citizens to depart the country “due to threats to US mission facilities and personnel.”

“The potential in Lebanon for a spontaneous upsurge in violence remains,” it said. “Lebanese government authorities are not able to guarantee protection for citizens or visitors to the country should violence erupt suddenly. Access to borders, airports, roads and seaports can be interrupted with little or no warning,” the statement said.

“Public demonstrations occur frequently with little warning and have the potential to become violent. Family, neighborhood or sectarian disputes often escalate quickly and can lead to gunfire or other violence with little or no warning.”

Americans currently in Lebanon “should understand that they accept risks in remaining and should carefully consider those risks,” it said, adding that those who chose to stay “should prepare to depart at short notice.”

The step had been under consideration since last week when President Barack Obama said he was contemplating military action against the Syrian government for its alleged chemical weapons attack last month that the administration said killed more than 1,400 people near Damascus.

The Obama administration is concerned that such action may spark reprisal attacks on US interests in the region. Hezbollah, an Iranian-backed group that has sent fighters into Syria to do battle on the Assad regime's side, is based in Lebanon.

The department noted that Hezbollah “maintains a strong presence in parts of the southern suburbs of Beirut, portions of the Bekaa Valley and areas in South Lebanon.”

“The situation remains tense, and sporadic violence involving Hezbollah or other extremist or criminal organizations remains a possibility in many areas of the country,” it said.

Shortly after the State Department announcement, about 150 people gathered for a protest near the US Embassy compound north of Beirut. Police kept the protesters confined to a square on a road leading to the heavily fortified embassy in the suburb of Awkar.

The protesters held banners that read “No to War” and “The American Embassy is an operations room for the war on Syria.” Another banner read: “Your rockets and fleets do not scare us.” Some of the protesters had painted their hands red to symbolise blood.

Dozens of riot police in full gear stood on guard, but there were no reports of any clashes.

In a separate advisory for Turkey, the State Department announced it would allow personnel at the Adana consulate to leave their posts and recommended that US citizens defer nonessential travel to southeastern Turkey.

The department also renewed its travel warnings for Iraq and Pakistan, advising Americans of continuing security concerns in those two countries. Both have been the subject of long-standing travel warnings.