Indonesian opposition leader Megawati Sukarnoputri rejected on Saturday President Susilo Bambang Yudhoyono's landslide re-election win and will challenge the results in court, a spokesman said.
Megawati's campaign will lodge a challenge to the results of the July 8 poll with the Constitutional Court, by alleging widespread irregularities including millions of people left off voter rolls, lawmaker Gayus Lumbuun said.
"Because there are still unresolved legal issues, we are rejecting the presidential election results from the KPU (election commission)," Gayus Lumbuun, from Megawati's Democratic Party of Struggle, said.
Official results announced by the commission on Saturday gave the liberal ex-general Yudhoyono 60.8 per cent of the vote, far ahead of ex-president Megawati with 26.8 per cent and Vice-President Jusuf Kalla with 12.4 per cent.
The Megawati campaign boycotted the official announcement of the results at the election commission office.
Kalla's campaign will also launch a Constitutional Court appeal over voter list irregularities, but has not yet decided whether to accept or reject the results, campaign spokesman Indra Piliang said.
"We have accepted the draft results signed by the KPU members ... (but) because we found irregularities in the voter list we'll file a legal challenge to the Constitutional Court," he said.
"According to the law, there have to be objective results before the declaration of the president and vice president-elect."
Yudhoyono denied there had been widespread fraud in the election but said opposing candidates had the right to launch "peaceful" challenges to the results.
"Our system and laws of course allow for those sides who still want to protest and file complaints," Yudhoyono said in a press conference broadcast on national television.
"In the public arena, voting issues of irregularities have emerged ... irregularities in elections don't always mean fraud. Nonetheless they have to be corrected, repaired and settled," he said.
The 59-year-old Yudhoyono, who defeated Megawati in Indonesia's first direct presidential election in 2004 on an anti-corruption platform, is credited with ensuring stability and economic growth.
Kalla's Golkar Party, the political vehicle of late dictator Suharto, has indicated it could join a Yudhoyono-led government but Megawati has maintained bitter opposition to the president.
Elite paramilitary police provided heavy security outside the election commission office, the road to which was blocked off by razor wire and armoured vehicles.
A spokesman for the election commission said the security measures were to prevent a repeat of bomb attacks on luxury Jakarta hotels on July 17, which killed seven people plus two suicide bombers.
Yudhoyono has come under fire for appearing to blame the attacks on political rivals aiming to overturn the election results, although police say the most likely perpetrator was a radical splinter faction of the Jemaah Islamiyah militant network.
The bombings, the first major attack in Indonesia since 2005, have broken years of quiet associated with Yudhoyono's rule but are seen as not likely to undermine forecasts of robust economic growth.