Two suspected Tamil rebels on a motorbike fatally shot the driver, and then forced the motorized rickshaw to stop. One of the soldiers in the back seat shot back but the rebels sprayed them with bullets, killing both of them instantly, said Brig. Daya Ratnayake, military spokesman.
A sergeant, a lance corporal and the soldier who was driving the vehicle were killed in the attack in Batticaloa, 230 kilometers (140 miles) east of Colombo, he said.
The attack took place as the chief of a European truce monitoring team, Hagrup Haukland, was discussing security issues with Tamil Tigers political wing leader S P Thamilselvan in the rebels' northern stronghold.
Complaining that the Tiger cadres face threats while traveling between northern and eastern areas, Thamilselvan warned that the group will use its own security and transport if the government fails to ensure their safe passage, a rebel Web site reported.
The Tigers warned that using their own transportation may disrupt the already fragile cease-fire.
Under a 2002 Norway-brokered truce, Tamil Tigers are allowed to travel freely, but without arms. The
However, after an April 2004 split within the rebel group, a number of cadres from the mainstream have been killed in the volatile east.
Last week a bus carrying 41 Tamil Tiger cadres with government military escort, narrowly escaped a land mine in eastern Welikanda area.
The government has accused the rebels of regularly killing military intelligence operatives and informants since the two sides agreed to a cease-fire in 2002. Lt. Col. Nizam Muthalif, a top intelligence officer, was shot dead in capital Colombo in May.
But the three soldiers killed Thursday represents the worst attack against Sri Lankan troops in months.
The 2002 cease-fire halted fighting in the two-decade civil war between the Tigers and the government that had killed about 65,000 people. Subsequent peace talks have been deadlocked over rebel demands for wide autonomy.
The government and the rebels signed a deal last Friday to share international tsunami aid.
