"It must be a joke," Rajapakse told AFP in response to the Tigers' ceasefire, which the rebels said would allow international aid agencies into the conflict zone to help civilians.
"What is the need for a ceasefire when they are running away? They should first lay down arms, surrender and let the people go," Rajapakse said.
The Liberation Tigers of Tamil Eelam (LTTE) said its ceasefire was "in the face of an unprecedented humanitarian crisis" and in response to international calls for a halt in fighting to allow help to reach trapped civilians.
"All of LTTE’s offensive military operations will cease with immediate effect," the rebels said in a statement.
A rebel spokesman, S. Puleethevan, said the Tigers would maintain their ceasefire only if the government reciprocated.
"The ceasefire is pur