The main Islamist rebel groups in Aleppo province, including Al-Nusra Front, have rejected the newly-formed Syrian opposition bloc saying they want an Islamic state, in an Internet video posted on Monday.

"We, the fighting squads of Aleppo city and province, unanimously reject the conspiratorial project called the National Coalition and announce our consensus to establish an Islamic state" in Syria, a spokesman announced in the video.

"We reject any external coalitions or councils imposed on us at home from any party whatsoever," he said.

The unidentified speaker sat at the head of a long conference table with at least 30 other men and a black Islamist flag on the wall behind him.

He listed 14 armed groups as signatories to the statement, including Ahrar al-Sham and Liwa al-Tawhid.

After the statement, another man held up a copy of the Koran, saying forcefully to the camera that it should be "your constitution."

"God is greatest," the group said in unison.

Abdel Jabbar al-Okaidi, the head of the main rebel Free Syrian Army (FSA) in the embattled northern city of Aleppo, told AFP that the statement did not represent the opinion of all rebel groups in the province.

"These groups represent a number of military factions on the ground and reflect their position, but not all military forces in Aleppo agree with this," the defected former colonel told AFP by phone.

"The military council has announced its support for the National Coalition and is collaborating with them," Okaidi added.

The National Coalition, formed in Doha on November 11, aims to present a united front to the international community and is lobbying for weapons and cash to help it topple the regime of Syrian President Bashar Assad.