The parties of both candidates in El Salvador’s surprisingly tight presidential runoff clash claimed victory late Sunday.

The parties of both candidates in El Salvador's surprisingly tight presidential runoff clash claimed victory late Sunday.

Pre-election polls indicated that ex-guerrilla leader Salvador Sanchez Ceren of the Farabundo Marti National Liberation Front (FMLN) would easily defeat Norman Quijano with the conservative ARENA party.

But with all of the returns tallied, the leftist candidate was leading by a tiny margin: 50.11 percent to 49.98, electoral authorities reported.

"We won the first round and now we have triumphed again in the runoff," Sanchez Ceren told enthusiastic supporters amid an explosion of fireworks.

But his ARENA counterpart was convinced its side had won.

Quijano claimed victory in a speech to supporters, and insisted that he would not allow "fraud of the Chavista or (Nicolas) Maduro style like in Venezuela."

He claimed that El Salvador's military was "aware of the fraud that is being perpetrated" by election authorities along with the FMLN.

Sanchez Ceren had conciliatory words for his rival.

"We can say right now that you have the doors open to work with us to move El Salvador forward," he said.

Election officials, likely expecting that vote results will be challenged and there will be calls for a recount, urged both sides to wait for final results.

"This tribunal recommends and orders that no party declare itself winner given such close results," said Supreme Electoral Tribunal president Eugenio Chicas in a TV and radio message.