SAN SALVADOR — Authorities declared El Salvador’s presidential runoff election too close to call late Sunday, with just a 0.2-percent margin separating a one-time Marxist guerrilla and the conservative former mayor of El Salvador’s capital.
Preliminary returns with more than 98 percent of votes counted showed Salvador Sanchez Ceren, the leftist candidate of the ruling Farabundo Marti National Liberation Front, the FMLN, less than 6,000 votes ahead of his conservative adversary, former San Salvador mayor Norman Quijano, out of about 3 million ballots cast.
It was a surprising result, considering that opinion polls in the weeks leading up to the election had put Quijano 10 to 18 percentage points behind Sanchez Ceren.
The president of El Salvador’s Supreme Electoral Tribunal, Eugenio Chicas, said the race was ‘‘extremely tight’’ and said neither candidate could claim victory.
‘‘This tribunal orders neither party to declare itself the winner, in light of results that are so close that only the final count can decide,’’ Chicas said, adding that ‘‘the margin is so close that we ask for prudence.’’
He said the final vote count would begin Monday.
Sanchez Ceren, 69, had been seen as the favorite to become the first true guerrilla to lead this Central American nation. Outgoing President Mauricio Funes was a journalist who was sympathetic to the FMLN rebels during the civil war but was never a guerrilla.
Quijano, 67, ran for the once long-ruling Nationalist Republican Alliance, known as ARENA, which lost the presidency to Funes in 2009.
Sanchez Ceren campaigned on a promise to deepen the outgoing government’s popular social programs and govern as a moderate. He said he envisioned ruling like Uruguayan President Jose Mujica, also a former guerrilla who formed an inclusive government.
Quijano accused the former guerrilla of appearing to want to lead the country like Venezuela’s late socialist president, Hugo Chavez, and he warned of a return of communism. He also promised to crack down on rising gang violence.
Sanchez Ceren was a top rebel commander who helped negotiate the 1992 peace accords that ended El Salvador’s 12-year civil war. During the war that killed 76,000 people, the United States supported the Salvadoran government against the FMLN to prevent communism from spreading in Latin America.
El Salvador is dealing with one of the highest murder rates in the world. A 2012 gang truce seemed to cut the country’s daily average of 14 dead by half, but the drop appears to have been short-lived.
Homicides, mostly of gang members, have risen again this year; police statistics show 501 murders the first two months of this year— a more than 25 percent increase over the same period of 2013. Many of the dead have turned up in mass graves.
During the campaign, Quijano lambasted Funes for negotiating with criminals because of the truce he struck between the Mara Salvatrucha and the 18th Street gangs. He promised to get tough on criminals, possibly militarizing public security.