Syrian rebel groups have issued a blistering attack on their Western-imposed "leadership", saying they no longer respected the Syrian National Coalition's authority.

The al-Qaida-linked al-Nusra Front led the charge of 13 groups who issued a joint statement slamming the Turkey-based coalition for not representing their interests.

The statement reflected the growing lack of unity between the political opposition in exile and the disparate rebel groups fighting President Bashar al-Assad's government.

It also highlighted the growing irrelevance of the coalition and its Western-supported Supreme Military Council, amid the increasing dominance of radical Islamist groups on the ground in Syria.

The rebel groups' statement called on all those trying to topple President Assad's government to unite under a "clear Islamic framework."

It said that the rebels will "not recognise" any future government formed outside Syria, insisting that forces fighting on the ground should be represented by "those who suffered and took part in the sacrifices."

But the rebels in Syria are also deeply divided and plagued by infighting, with many groups blaming al-Qaida militants in their ranks for the West's reluctance to intervene militarily or give them the advanced weapons they need.

There is also growing concern that the dominant role that radical Islamists are playing is discrediting the rebellion.

The rebel announcement came almost two weeks after the SNC elected Ahmad Saleh Touma as the opposition's interim prime minister.

Meanwhile, a team of UN chemical weapons inspectors have arrived in Damascus to continue investigating the use of chemical weapons.

The visit of the six-member team, led by Swedish expert Ake Sellstrom, follows a report by the inspectors after their previous trip in September, which said nerve agent sarin was used in an August 21 attack near the capital Damascus.

The UN said on Tuesday that inspectors will use their new visit to gather evidence from the alleged chemical weapons attack on March 19 on the village of Khan al-Assal outside Aleppo, which was briefly captured by the rebel groups in July.