"In Syria meanwhile, the killing continues. This must stop," said the UN secretary-general.

"I call on the Syrian leadership to deliver on its commitments and to allow our UN humanitarian assessment team and the human rights fact-finding mission mandated by the Human Rights Council in.

"It's time to see progress here. We cannot go on like this," said Ban.

Human rights groups say that more than 1,300 civilians have been killed and thousands more arrested since anti-regime protests started nearly four months ago.

In their latest crackdown on protestors this week, Syrian troops killed more than 20 people in an assault on the flashpoint central city of Hama on Tuesday, human rights activists said.

The United Nations has been pressing for access to the strife-torn country, but to no avail so far.

The International Committee of the Red Cross has been granted access recently, but only after its president Jakob Kellenberger travelled to Syria personally to make the request.

Copyright AFP (Agence France-Presse), 2011