WASHINGTON (AFP) - The United States has evidence that groups linked to Syria are "playing a much more active role in fanning the flames" in Lebanon, a senior US official charged Friday.

"We're seeing now some evidence of those groups that are linked to Syria that are in Lebanon right now are taking a much more active role in fanning the flames of violence," State Department spokesman Sean McCormack said.

The evidence includes sightings of individuals and groups linked to Damascus starting to "engage on the ground, out in the streets and ... at least encouraging these acts of violence," McCormack said.

"We've had a lot of questions about Iran and Syria and the linkages between Hezbollah, and are they playing a role in the current crisis right now? Up until this point, I hadn't been able to say that," McCormack told reporters.

But, he said, Washington has no hard evidence that Iran was stoking the violence in Lebanon, which has seen at least 11 people killed and dozens wounded since Thursday and has pushed the country dangerously close to all-out civil war.

A State Department official who asked not to be named said the evidence shows the Syrians "are piling on, taking advantage of the situation," rather than having initiated the violence.

But the official added "you never probably will fully know all the motivations here, whether or not there was any Syrian hand in the initial actions that Hezbollah took."

Asked what action Washington could take against Syria, the official replied: "We're pretty sanctioned up on Syria at the moment. There are always options, but I'm not aware of anything else right now."

Beirut has been rocked since Thursday by street battles since Hezbollah chief Hassan Nasrallah said a crackdown by the pro-Western government on his group, which is backed by both Iran and Syria, was a declaration of war.

A political standoff, which first erupted in November 2006 when six pro-Syrian ministers quit the cabinet, has left Lebanon without a president since November, when pro-Syrian Emile Lahoud stepped down.

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