China said Thursday it held talks with a key Syrian opposition group this week, amid fierce criticism of its decision to block a UN resolution condemning a bloody crackdown in the Middle East country.

China and Russia drew international ire for blocking the UN Security Council resolution on Saturday, with Washington calling their rejection a "travesty" and another Syrian opposition group saying they had handed President Bashar al-Assad's regime a "licence to kill".

Chinese foreign ministry spokesman Liu Weimin said the visit by the National Coordination Body for Democratic Change (NCB) had "long been scheduled" and was not linked to China's controversial veto.

NCB representatives told Chinese officials they would like Beijing "to play a bigger role for an early resolution to the Syrian crisis," Liu said.

But the NCB, one of the main opposition factions in Syria, staunchly opposes foreign military intervention in the conflict -- which is in line with China's long-standing policy of non-interference in other nations' internal affairs.

The other main opposition group, the Syrian National Council (SNC), is widely regarded as the most inclusive of Syria's opposition alliances and has previously called for foreign military intervention.

The SNC blasted China and Russia over their double veto and said they had given a "licence for the Syrian regime to kill without being held accountable."

Liu said Vice Foreign Minister Zhang Zhijun met members of the NCB to discuss "the situation" in Syria. He urged both sides of the conflict to "cease all violence... and avoid casualties among civilians".

Liu reiterated that China was "the friend of all Syrian people" and did not "seek its own interests on the Syrian issue".

The NCB was in Beijing from February 6 to 9 at the invitation of the Chinese People's Institute of Foreign Affairs, a government-backed foreign policy organisation.

China said Tuesday it was considering sending envoys to the Middle East to help resolve the conflict, after Russia sent its top diplomat Sergei Lavrov to Damascus.

Thirteen countries voted for the UN Security Council resolution, which aimed to give strong backing to the Arab League's plan to end a deadly government crackdown on protesters.

More than 6,000 people have died in nearly a year of upheaval in Syria, as Assad's hardline regime seeks to snuff out a revolt that began with peaceful protests in March 2011 amid the Arab Spring.