Israeli-built Kfir jets attacked a Tiger position close to the frontline of fighting in the northern district where rebels 11 days ago launched a push to retake their former stronghold, the military said.
In Colombo police said they had foiled a rebel attack after defusing a 15-kilogram (33 pound) mine rigged to a vegetable seller's bike in a busy market area.
Officials said they believed the fragmentation device may have been aimed at a Sri Lankan legislator.
It followed an attack last week on Pakistan's top envoy who escaped without injury while seven other people were killed.
The military reported sporadic rebel mortar and grenade attacks in the northeast overnight before they launched air strikes against the Tamil Tiger position in the Jaffna peninsula.
"Just after the air attack, we could hear secondary explosions," a military official in the peninsula said. "It is most likely that their ammunition dump was hit.
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The peninsula, home to some 350,000 civilians, has been cut off