Sri Lankan officials say suspected Tamil rebels have killed four farmers in the eastern part of the country.

Officials say rebels ambushed the farmers Thursday in the district of Polonnaruwa. The attack happened near a jungle area where Tamil rebels have been fighting Sri Lankan troops. The rebels had no immediate comment on the shootings.

In another indicent, Sri Lankan police say they found a powerful, unexploded landmine inside a shop near Colombo Thursday. Police say the bomb was being hidden for use in a future attack. Five suspects were detained after the device was seized.

On Wednesday, Sri Lanka's air force said it destroyed the rebels' naval base in the northeastern district of Mullaithivu.

Tamil rebels denied that Sri Lankan jets struck their naval headquarters.

The rebels said the warplanes actually hit an institute that makes prosthetic limbs for landmine victims. They said the air strike killed two civilians and wounded and several others.