Clashes continued between government troops and separatist Tamil Tiger rebels amid growing concern over food shortages in parts of the disputed northeast cut off from the rest of the country.
The team of monitors from five Nordic nations said "intensive military operations" had restricted their work and were quitting strife-hit areas to return to Colombo.
Diplomats from the US, European Union, Norway and Japan met President Mahinda Rajapakse at his official residence here Monday to express growing concern at the violence which has claimed more than 1,500 lives since December.
They have been pressing for an immediate halt to the bloodshed and a resumption of talks put on hold in April 2003 by the Tiger guerrillas.
A ship with up to 2,600 tonnes of food and medicine due to leave Colombo for the island's far north was also delayed Monday because of bad weather, the military said.
"We could not complete loading yesterday because of rains," said defence ministry spokesman Brigadier Prasad