WASHINGTON — The Iraqi branch of al Qaida, seeking to exploit the bloody turmoil in Syria to reassert its potency, carried out two recent bombings in the Syrian capital, Damascus, and likely was behind suicide bombings Friday that killed at least 28 people in the largest city, Aleppo, U.S. officials told McClatchy.

The officials cited U.S. intelligence reports on the incidents, which appear to verify Syrian President Bashar Assad's charges of al Qaida involvement in the 11-month uprising against his rule. The Syrian opposition has claimed that Assad's regime, which has responded with massive force against the uprising, staged the bombings to discredit the pro-democracy movement calling for his ouster.

The international terrorist network's presence in Syria also raises the possibility that Islamic extremists will try to hijack the uprising, which would seriously complicate efforts by the United States and its European and Arab partners to force Assad's regime from power. On Friday, President Barack Obama repeated his call for Assad to step down, accusing his forces of "outrageous bloodshed."

The U.S. intelligence reports indicate that the bombings came on the orders of Ayman al Zawahiri, the Egyptian extremist who assumed leadership of al Qaida's Pakistan-based central command after the May 2011 death of Osama bin Laden. They suggest that Zawahiri still wields considerable influence over the network's affiliates despite the losses the Pakistan-based core group has suffered from missile-firing CIA drones and other intensified U.S. counterterrorism operations.

U.S. officials said that al Qaida in Iraq, or AQI, began pushing to become involved in Syria as Assad's security forces and gangs of loyalist thugs launched a vicious crackdown on opposition demonstrations, igniting large-scale bloodshed. Growing numbers of lightly armed army deserters and civilians have joined an armed insurrection, and perhaps thousands of people have been killed.

Zawahiri finally authorized AQI to begin operations in Syria, the officials said, in what's believed to be the first time that the branch has operated outside of Iraq.

"This was Zawahiri basically taking the shackles off," said a U.S. official with access to the intelligence reports. Like others interviewed for this story, he spoke on condition of anonymity because the issue involves classified information.

U.S. officials believe that the Sunni Muslim AQI was looking to expand beyond Iraq, where it has been stepping up attacks on majority Shiites. In Syria, Assad heads a regime dominated by Alawites, a minority Shiite Muslim sect that has ruthlessly ruled the Sunni Muslim-majority country since Assad's father seized power in a 1963 coup.

While the extent of AQI's presence in Syria is unknown, U.S. officials believe that it's too small to have a decisive effect on the conflict. Although al Qaida and its affiliates may have sought to play roles in other Arab Spring uprisings, this appeared to be the first time that the network had successfully done so.

"This has less to do with the targets and more to do with the opportunity," the U.S. official said.

Fears of AQI's widening ambitions are one reason why the United States wants to maintain good relations with Iraqi Prime Minister Nouri al Maliki despite concerns over his increasingly autocratic rule, a second U.S. official said.