A veteran legislator and former political detainee returned his party to power in Grenada on Tuesday after 13 years in opposition, according to preliminary election results.

The apparent win by Tillman Thomas' National Democratic Congress is a stunning setback for Prime Minister Keith Mitchell's conservative New National Party, which was seeking an unprecedented fourth consecutive term in legislative elections.

Grenada's Elections Office released a statement saying that their preliminary count showed the National Democratic Congress winning 11 of 15 seats. The ruling New National Party had four seats. The final count will be certified and announced on Wednesday.

The leader of the party that controls a majority of seats in Parliament becomes prime minister, the country's top elected official.

The vote came 25 years after Grenada weathered a coup and U.S. military invasion.

The ruling party was apparently hurt by allegations of "autocratic" tendencies leveled at Mitchell, who took office in 1995.

Stunned party spokesman Terrence Forrester conceded defeat.

"It was a surprise. The party will now engage in deep introspection," Forrester told reporters.

Analysts had predicted a close election in the southern Caribbean island of 100,000, giving the edge to Mitchell's party, which narrowly defeated the National Democratic Congress in 2003.

Opposition supporters danced to calypso music and honked car horns at impromptu victory celebrations in St. George's.

"I'm feeling happy, very joyous," said local preacher John St. Bernard. "I wish this had happened 10 years ago."

Thomas, who could not immediately be contacted Tuesday night, has promised to create jobs, lower the cost of living and better manage Grenada's economy.

Thomas was in prison as a political detainee of the Cuba-aligned government of Maurice Bishop when U.S. forces invaded the country in 1983.

U.S. and regional troops stormed Grenada after the leftist government was overthrown and its leaders executed by an even more hard-line Marxist faction.