China has called for an end to violence in Syria after the regime of Bashar al-Assad sparked international outrage by blocking aid from reaching a battered neighbourhood in the flashpoint city of Homs.

As more bloodshed was reported across Syria, Britain and Turkey joined the international outcry accusing the regime of committing a crime by barring Red Cross convoys from entering Baba Amr for the second day.

China, which twice joined Russia in blocking UN Security Council resolutions against Syria's lethal crackdown on dissent, urged all parties in Syria to "unconditionally" end the violence.

Xinhua news agency cited a foreign ministry statement attributed to an unnamed official calling for dialogue between the Syrian regime and those expressing "political aspirations".

But the official reportedly added: "We are opposed to anyone interfering in Syria's internal affairs under the pretext (of) humanitarian issues."