The International Red Cross has said one of its convoys in Syria has been blocked from entering the shattered district of Baba Amr in Homs.

The mission had hoped to deliver much needed food and medical supplies and evacuate the sick and wounded after weeks of Syrian government bombardment.

Britain’s Prime Minister David Cameron demanded immediate humanitarian access.

“This is the very least that must happen to bring immediate relief to those who are wounded or dying but it is far from enough,” he said in Brussels. “The world must come together to condemn the killing so I say to the Russians and to the Chinese, look hard at the suffering from Syria and think again about supporting this criminal regime.”

Meanwhile Russia’s Prime Minister Vladimir Putin appeared to distance himself from Syria’s regime saying he had no special relationship with President Assad.

“Our goal is not to support this or that party in the conflict, nor to support the government or the armed opposition. No, our goal is overall reconciliation in Syria,” Putin said.

But that seems a long way off, with bloodshed continuing.

In Homs province activists said at least 13 people died when Syrian security forces fired a mortar on anti-Assad protesters in Rastan.

The UN says the regime has killed more than 7,500 civilians since the revolt began last March.