On Thursday, ceasefire monitors said that both the government and rebels had openly violated the 2002 truce.

Mr Schwartz called on all parties to the conflict to cease hostilities.

He said: "In parts of the north and east, the tsunami recovery process has ground to a halt and significant investments in reconstruction, so generously supported by donors around the world, are now imperilled."

Cut off

Eric Schwartz is the deputy to special envoy for tsunami recovery, former US President Bill Clinton.

Mr Schwartz stressed that many thousands of civilians were at risk and cut off from regular supplies of food and assistance.

"It is critical that all parties to the conflict ease current restrictions on access to affected populations," he urged.

Large-scale violence in Sri Lanka's 20-year civil war reared in late July. Hundreds of people have been killed this year.

More than 60,000 people have died since the rebels began their fight the 1970s for a separate homeland for minority Tamils in the north and east.