A commander officer in the Free Syrian Army (FSA) has confirmed that fierce clashes had broken out on Friday night in the eastern city of Deir al-Zor between the Syrian rebels and the Al-Assad regime troops.

"40 military officers including a first-Lieutenant have defected with their weapons while fierce fighting  erupted in Deir al-Zor airport as the FSA fighters were trying to control over it," the defected officer said adding that they have confirmed information that numbers of the government troops who fled to desert are expected to be doubled.

A Syrian fighter pilot on a training mission flew his MiG-21 warplane to Jordan on Thursday and asked for political asylum, the first defection of an air force pilot with his plane during the 15-month uprising against President Bashar Assad.

The pilot, identified as Col. Hassan Hammadeh, removed his air force tag and kneeled on the tarmac in prayer after landing his plane at King Hussein Air Base in Mafraq, Jordan, 45 miles (70 kilometers) north of Amman, a Jordanian security official said.

The defection was a triumph for the rebels who are fighting to overthrow Assad. The air force is considered  loyal to the government, and the defection suggests some of Syria's most ironclad allegiances are fraying. A spokesman for the rebel Free Syrian Army, Ahmad Kassem, said the group had encouraged the pilot to defect and monitored his activity until the jet landed safely in Jordan. He said the pilot was based in southern Syria.

The French foreign ministry called Friday for the Syrian military to desert en masse the day after a Syrian air force colonel defected after landing his MiG fighter in Jordan.

The United States Thursday also welcomed the defection of a Syrian fighter pilot to Jordan as a "courageous" act and a "significant moment" in the 16-month conflict in Syria. "This is how these things start," said State Department spokeswoman Victoria Nuland.

"It is obviously a significant moment when a guy takes a $25 million plane and flies it to another country."  Nuland said US officials had been in touch with the Jordanian government, which had confirmed that a Syrian MiG had landed in Jordan with the pilot on board. He had requested and been granted political asylum.

The White House said the Syrian pilot would not be the last person to do the "right thing" and desert Damascus's armed forces.

The Syrian government of President Bashar al-Assad has denounced the pilot of the MiG fighter plane as a "traitor" and demanded the jet be returned.

"We welcome this pilot's decision to do the right thing," US National Security Council spokesman Tommy Vietor told AFP.

"We have long called for the military and members of the Syrian regime to defect and abandon their positions rather than be complicit in the regime's atrocities.

"This is just one of countless instances where Syrians, including members of the security forces, have rejected the horrific actions of the Assad regime, and certainly it will not be the last."

The US believed hundreds of troops had already defected from the ranks, Nuland said, adding the pilot's act was "extremely courageous."