The man was killed in a clash with ruling party activists in northwestern Sri Lanka, the third politically-related death in the run-up to the vote on January 26.
Supporters of the main opposition candidate, former army chief Sarath Fonseka, were attacked in the town of Wariyapola while they were putting up election posters, police said.
"One man was killed and several others sustained injuries," police Deputy Inspector General Anura Senanayake said. "There had been 694 poll-related incidents of violence since nominations were handed in a month ago."
He said 289 suspects had been arrested in connection with the incidents, but declined to say which party was responsible for most of the violence.
President Mahinda Rajapakse, who is running for re-election, has ordered a security crackdown to quell unrest, his spokesman Chandrapala Liyanage said Sunday.
Opposition activist Kusuma Kuruppuarachchi, 60, was the first to be killed in the poll campaign when she was shot in the southern to