Early returns from El Salvador's congressional elections give a narrow lead to a leftist party of former rebels.

With around 20 percent of votes counted from Sunday's elections, the Farabundo Marti National Liberation Front, or FMLN, is slightly ahead of President Tony Saca's conservative ARENA party.

An exit poll released on national television suggests the FMLN will secure 34 seats in El Salvador's 84-member Congress. The same poll puts the ruling ARENA party one seat behind with 33.

The FMLN was a guerrilla group during El Salvador's civil war, and became a political party under a 1992 peace deal.

El Salvadorans also voted for mayors in 262 races, including in the capital, San Salvador.

Some information for this report was provided by AFP, AP and Reuters.