Leftist political neophyte Pedro Castillo maintains a narrow lead over Keiko Fujimori - the daughter of disgraced former President Alberto Fujimori - with just 0.7 percent of the votes from last weekend's presidential runoff still to be counted, Peru's ONPE electoral agency said Thursday.

The 51-year-old schoolteacher from one of Peru's poorest regions has an edge of 50.2 percent to 49.8 percent, or a little more than 68,000 votes, over Fujimori, 46.

Though the ballots left to be tabulated exceed the difference between the candidates, the bulk of them come from districts where Castillo has been winning by a margin of 67 percent to 33 percent.

Special electoral boards are still reviewing 608 tally sheets that have been challenged. More than half of the challenges pertain to sheets from areas where Castillo prevailed with large majorities.

And the National Electoral Court (JNE) must grapple with a motion brought by Fujimori's right-wing Fuerza Popular party to throw out nearly 200,000 votes from precincts carried by her opponent.