Election officials confirmed the governing United People's Freedom Alliance party (UPFA) and its allies had won control over a new 35-member provincial council in the eastern coastal region.
Opposition parties and monitoring rights groups, however, complained of widespread irregularities, including harassment by Tamil Tiger defectors now allied to hawkish President Mahinda Rajapakse.
Rajapakse hailed the vote as "a clear mandate for peace through the defeat of terrorism, the strengthening of democracy and the development of the country.
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The region, once home to several Tamil Tiger enclaves, was brought under government control after heavy fighting last year, and Colombo is determined to show normality has returned.
The polls were overshadowed by the rebel sinking of a navy cargo ship in Trincomalee port hours before voting started on Saturday, as well as a bomb attack in the town of Ampara late Friday that killed 12 civilians.
But the government boasted that the Liberation Tiger