In less than 24 hours, rebels used surface-to-air missiles to strike down two aircraft in northern Syria, marking a turning point in their war with forces of President Bashar al-Assad.

Since the end of July, the Syrian regime has used fighter jets to try to suppress a growing insurgency. The air force has frequently bombarded rebel-held areas across the country, causing high casualties.

But on Wednesday morning, rebels shot down a warplane in the northern province of Aleppo, an AFP reporter said.

The warplane crashed after it was hit by a massive explosion, a tower of thick black smoke rising into the sky, said the reporter, who was just a few kilometres (miles) away.

The previous day insurgents had downed an army helicopter for the first time.

"It's a turning point," said Riad Kahwaji, expert at the Institute for Near East and Gulf Military Analysis (INEGMA).

"If the Syrian air force starts losing several aircraft every day, that will be a significant turning point because the regime will lose its superiority and will no longer be able to use its main means of delivering strong fire power effectively," Kahwaji said.

The jet fell on an olive grove a kilometre (less than a mile) away from the village of Tourmanin, north of the embattled city of Aleppo.

Wednesday's attack, claimed by a rebel Free Syrian Army group, occurred near the Sheikh Suleiman base, the last garrison in government hands between Syria's second city and the Turkish border.

Dozens of rebels rushed to the scene minutes after the plane was shot down, crying out "Allahu Akbar!" (God is Greatest).

Children rummaged among the smouldering debris, as the stench of kerosene and burning plastic rose. Some teenagers picked up pieces of the plane's broken wings, others played with ammunition.

The Britain-based Syrian Observatory for Human Rights, a watchdog that relies on a network of activists and medics on the ground, confirmed that the jet had been brought down with a missile.

While some witnesses gave a similar version, others said rebels used an anti-aircraft gun to strike the jet.

It appeared more likely that the rebels used a missile as the plane had been flying at a high altitude.

Rebels in Tourmanin said insurgent members of the Ahrar Daret Ezza group, whose name means the Free People of Daret Ezza, a nearby village, were responsible for the strike.

"The plane had the time to drop its bombs, just before it crashed," one witness said.

The crash caused an explosion that was easily heard several kilometres away.

The two pilots in the plane ejected before the crash, with one of them captured immediately after making a parachute landing, witnesses said. The fate of the second pilot is unknown.

The jet was the second government aircraft to have been shot down by rebels using missiles in less than 24 hours.

In the same area on Tuesday, insurgents downed the army helicopter with a ground-to-air missile, in what the Observatory said had the potential to change the balance of military power in the 20-month old conflict.

The gunship had been on a strafing run near Sheikh Suleiman.

Little more than a week ago, the rebels seized tanks, armoured vehicles, artillery, 120-mm mortars and rocket launchers when they took the regime forces' sprawling Base 46, about 12 kilometres (eight miles) west of Aleppo.

Rebel commander General Ahmed Faj said on Friday that the rebels also seized surface-to-air missiles from the base.

"If the rebels have a significant arsenal of surface-to-air missiles, like the well-known Stingers that decimated Russian helicopters and jets in Afghanistan, Assad's army will lose part of its control of the sky," Syria expert Fabrice Balanche said.

"Rebel-held areas will become safe, and insurgents will be able to go on the offensive without fearing the aerial threat."

"It's a red line the rebels and their supporters have crossed," Balanche added.

Syria's revolt is supported by Turkey, several Gulf states and the West, while Russia, China and Iran offer assistance to Assad's regime.

"Now the Russians will certainly give the Syrians more sophisticated equipment," said Balanche.