* Former rebel proxy wins 30 out of 38 seats
* Rajapaksa suffers worst defeat since he assumed office
* Victory could reignite calls for autonomy
Sri Lanka's main ethnic minority Tamil party secured a landslide victory in a provincial poll that has threatened to rekindle animosity between the government and Tamils, four years after the military crushed separatist rebels and ended a 26-year war.
The Tamil National Alliance (TNA), the former political proxy of the defeated Tamil Tiger rebels, won 30 seats in the 38-member provincial council in the former northern war zone, election officials said on Sunday.
President Mahinda Rajapaksa's ruling coalition won 7 seats, while a Muslim party won one.
It was the first provincial council election in the north in 25 years and was held after the government came under international pressure to restore democracy.
Defeat for the government, the most humiliating set-back for Rajapaksa since he assumed office in 2005, is largely symbolic.
But the TNA's victory shows that the defeat of the rebels in 2009 did nothing to dampen calls for autonomy among Tamils, who make up about 14 percent of Sri Lanka's 20 million people.
"This is a strong message to the international community to say that Tamils need a political solution," said a voter in the northern town of Jaffna, computer studies lecturer T. Sivaruban.
"It could be a separate state or power sharing within a united Sri Lanka," said Sivaruban, 33.
The TNA won more than 84 percent of the votes in Jaffna, once the heartland of the rebel movement, 81 percent in Kilinochchi, the de-facto capital of the separatists, and 78 percent in Mullaitivu, where thousands of civilians were said to have been killed in May 2009, when government forces moved in to defeat the rebels.
"It's a great vindication of the political stand we've taken and our people have stood up without bowing down to violence and intimidation," M. A. Sumanthiran, a TNA legislator, told Reuters. "Now the president has to bow down to this verdict."
A foreign observer said the election commission had done a very good job inside the polling centres, though it did not have any control over what went on outside, where some voters reported attacks and intimidation.
The government has accused the TNA of renewing calls for a separate state through its push for the devolution of power. The TNA says it wants devolution in a united Sri Lanka, not a separate state.
Many voters have called for the return of land that they say the army has occupied. The are also calling for the withdrawal from the north of the army, which was accused of human rights abuses in the final stages of the war.
Some voters have also called for a separate state, for decades the goal of the Liberation Tigers of Tamil Eelam, who launched their war in 1983 to end what Tamil activists saw as systematic discrimination by Sri Lanka's Sinhalese majority.
Election officials said they received "plenty" of complaints, including complaints of intimidation of voters during the polling, but turnout was about 68 percent.
The military has rejected any suggestion of involvement by the security forces in election-related violence of any sort.
Rajapaksa has a majority of more than two-thirds in the national parliament and controls the eight other provinces.
The president has faced international pressure to bring to book those accused of war crimes committed at the end of the war, and to boost reconciliation efforts.
His government has rejected accusations of rights abuses and Rajapaksa in July ordered an inquiry into mass disappearances, mostly of Tamils, at the end of the war.