Police said gunmen killed the men in the town of Sammanturai on Monday morning, adding they suspected members of the Liberation Tigers of Tamil Eelam (LTTE) were involved.
However, no one has yet claimed responsibilty for the killings.
The attack came as security was stepped up in Sri Lanka's Eastern Province on Sunday, following inter-communal clashes between Tamils and Muslims.
A night curfew was imposed in the Muslim town of Muttur amid fears of renewed clashes, following the killing last week of another two Muslim men.
Four policemen were wounded on Saturday as they tried to separate mobs in the latest fighting, which was sparked by the detention of two Muslim fishermen by suspected Tiger rebels.
Muslim leader Rauf Hakeem travelled on Monday to Sammanturai in an attempt to defuse tension.
Hakeem said he would try to arrange better security for villages in the Muttur region.
He will also discuss the issue of harassment of Muslims in the town with security authorities and the Scandinavian team, monitoring a truce between the government and rebels.
Muttur, 270km north-east of the capital Colombo, has a large concentration of Muslims, who are Sri Lanka's second largest minority after Tamils.
The latest unrest came as Norway expressed grave concern over a spate of political slayings and violations of the peace truce by Tamil Tigers.
The government has waged a
brutal war against Tamil rebels
The LTTE pulled out of peace talks with the Sinhalese-dominated government on 21 April.
They demanded an interim political set-up in which they have a majority stake before they re-entered the negotiating process.
International rights groups and the US government have slammed the Tigers for killing their political opponents despite the truce.
Sri Lanka has been gripped by civil war for 20 years.
Minority Tamils want a separate homeland in the north and east of the island.
However, the Sinhalese government has waged a brutal war on the rebels to keep Sri Lanka united.
Meanwhile, the island's Muslims have been caught between a rock and a hard place.
Despite speaking Tamil as a mother tongue and living in Tamil-dominated areas, Muslims have mainly supported the Sinhalese government.
As a consequence, they say, the Tamil Tigers have embarked on a cleansing campaign against Muslims in Tamil majority areas.