(Updates with tight vote, runoff vote certain)
By Brian Ellsworth
BOGOTA, May 25 (Reuters) - Colombian President Juan Manuel Santos and right-wing challenger Oscar Ivan Zuluaga were locked in a tight election race on Sunday and will face each other in a runoff next month.
With results in from 84 percent of voting tables, Zuluaga had 29 percent support and Santos trailed with 25.5 percent. They had needed 50 percent for victory so will now go to a runoff on June 15.
The election was largely seen as a plebiscite on Santos' strategy of negotiating a peace deal with Marxist guerrillas to end a 50-year-old war that has killed some 200,000 people.
Zuluaga accuses Santos of pandering to terrorists and has suggested he would scrap the talks in favor of U.S.-backed military campaigns similar to those led by his mentor, former President Alvaro Uribe.
"Security is important to us; we are 100 percent with Zuluaga," said Jose Gomez, 39, as he left a Bogota polling station with his wife and daughter.
Uribe fell out with Santos, 62, when the president launched peace talks with the Revolutionary Armed Forces of Colombia (FARC) instead of sticking to the eight-year strategy of forcing the group's surrender on the battlefield.
Santos appeals to Colombians who hope the guerrillas will lay down arms after seeing top leaders killed and their numbers halved to about 8,000 fighters.
The talks in Cuba have yielded agreements on three items of a five-point agenda, including one deal just signed in which the FARC agreed to step away from the drug trade.
But Zuluaga has galvanized conservative Colombians who believe the talks will fail like three similar attempts since the 1980s, including a 1999 peace deal that let the FARC bolster its ranks and boost involvement in drugs. (Additional reporting by Peter Murphy and Julia Symmes Cobb; Editing by Helen Murphy and Kieran Murray)