As heavy fighting continues in Syria, an envoy to President Bashar al-Assad has visited Beijing in a bid to build on diplomatic relations with China, one of Syria's strongest allies.

Assad's political and media adviser, Bouthaina Shaaban, will meet China's foreign minister Yang Jiechi for talks.

Both China and Russia have come under intense criticism from Western powers and the Arab world for their support of the Assad regime despite the civil war that has led to an estimated 20,000 deaths in 18 months.

Both countries vetoed the UN Security Council resolutions, designed to exert pressure on the Assad regime, prompting Kofi Annan to quyit as peace envoy. Beijing said it was trying to prevent more violence.

Foreign ministry spokesperson Qin Gang said: "China has always actively promoted its work between the Syrian government and the opposition in a balanced way to achieve a political solution on the Syria issue."

Annan and US officials were in Beijing to persuade China to back the UN resolutions but the country was unlikely to change its policy.