A defence ministry spokesman said no new strikes were launched on Thursday; but the rebels claimed that at least a dozen people were killed in the air raids near the northeastern port of Trincomalee.
The air strikes followed an attempted assassination of Lt- General Sarath Fonseka, the Sri Lankan army chief, by a female suicide bomber on Tuesday.
Ulf Henricsson, the Swedish head of the cease-fire monitoring team, said the truce was still valid despite the hostilities.
"Certainly, we still have a valid cease-fire. No one has abrogated it," he said. But he also said that "what is going on is a serious violation of the agreement."
The rebels, formally known as the Liberation Tigers of Tamil Eelam, or LTTE, said 40,000 people, almost all Tamils, have fled their homes in the northeast and that the rebel movement would seek to provide them shelter.
A rebel statement said: "LTTE had protected Tamil people....for many years. Today, Tamil people are seeking and expecting protection from our movement."
The Tamil Tigers fought a two-decade long civil war in an attempt to create a Tamil homeland in north-eastern Sri Lanka, claiming discrimination by the majority ethnic Sinhalese. A Norway-brokered truce halted large-scale fighting in 2002, but disputes over post-war power-sharing have hindered peace talks, and sporadic violence has raised tensions in recent months.