The general staff also denied reports that U.S. military units were sent to the Turkish-Syrian border.

The United States has a number of military personnel based at Incirlik Air Base in Adana as well two other bases.

Al Qaeda leader urges support of Syrian rebels

Al Qaeda leader Ayman al-Zawahiri called on Muslims everywhere to support Syrians in their fight against al-Assad's "murderous, cancerous regime."

In a long video posted on jihadist websites, al-Zawahiri said Muslims should spare nothing to help free the Syrians. He also encouraged the Syrians to rise up against the government.

"It is the right of Syrians to protect themselves in all ways possible from injustice, murder, killing and bombardment," al-Zawahiri said.

"He whose house is destroyed, children are killed, and brothers are tortured has every right -- all right -- to use every legitimate way to keep aggression away from him."