Jets dropped at least five bombs near the rebel headquarters in Kilinochchi after the town was overflown once by a propeller-driven spotter plane just after dawn.
"The air force carried out two bombing sorties over Kilinochchi and Mullaitivu," a military source in Colombo said referring to two northern areas held by the Tigers.
There were no immediate reports of casualties or damage from Friday's raids.
S Puleedevan, head of the rebel peace secretariat, said: "We are still assessing the situation and our response. It looks as though the government is ready for war."
The Tigers denied responsibility for a claymore mine ambush on Thursday that blasted a bus on a remote road near the rebels territory killing 64 civilians. It was the worst such incident since a 2002 ceasefire.
Diplomats fear that civil war may
again erupt in Sri Lanka
Sri Lanka Monitoring Mission (SLMM), increasingly caught in the middle of the the conflict, condemned the attack but said they also regretted the government retaliation.
"SLMM still hopes that the parties of the ceasefire agreement will respect the agreement and get back to the negotiating table," said SLMM spokesman.
Diplomats and analysts said the bus attack had all the hallmarks of the Tigers. Few have believed their recent denials of responsibility for similar attacks on the military.
More than 500 people have died since early April as a 2002 ceasefire fades into low intensity conflict.
The Tigers, who want a separate state for minority Tamils in the island's north and east, refused to meet a government delegation for talks in Norway last week.
Diplomats say neither the government nor the rebels have shown enough flexibility, but some say the situation is now spiralling out of control and that it may soon be too late to stop a return to a two decades-old war that has killed more than 64,000 people.