Sri Lanka's opposition on Monday said it planned to mount a legal challenge to the government's weekend win in key local elections in the east of the island.
The opposition said President Mahinda Rajapakse's party and his allies, including Tamil Tiger rebel defectors, used "terror" tactics to bully voters and intimidate rivals. The government insists the polls were free and fair.
"The opposition parties faced the terror of the government and a former terrorist group," Sri Lanka Muslim Congress (SLMC) leader Rauf Hakeem told reporters.
"The end result is virtual daylight robbery of voters in the east. We are collecting evidence to go before the courts and will start a street agitation campaign," said Hakeem, whose party is allied with the main opposition United National Party.
UNP leader Ranil Wickremesinghe said Sri Lanka was "taking another step towards dictatorship."
The polls were the first to be held in 20 years in the tsunami-hit and ethnically-mixed eastern districts of Batticaloa, Trincomalee and Ampara.
Parts of the region were controlled by the Liberation Tigers of Tamil Eelam (LTTE) until the government forced them out in a fierce offensive last year.
The president now wants to partially devolve power in the east from his ethnic Sinhalese-dominated government to ethnic Tamil allies in the Tamil People's Liberation Tigers (TMVP), made up of rebels who switched sides.
The TMVP are accused of continuing to carry guns, using child soldiers and intimidating locals. Their leader, who goes by the nom-de-guerre of Pillayan, wants to be the east's new chief minister.