By Petar Komnenic
PODGORICA (Reuters) - Montenegro's opposition refused on Monday to accept a third term for President Filip Vujanovic, a stance that could trigger instability in the tiny Adriatic state seeking European Union membership.
Montenegrins were still awaiting the official results of Sunday's closely fought election for the largely ceremonial post that both sides said they had won.
Both Vujanovic and his opposition challenger, former diplomat Miodrag Lekic, claimed victory. The state electoral commission has until 8 a.m. (0600 GMT) on Tuesday to announce the official result.
The dispute looked set to usher in an unstable period for the ex-Yugoslav republic of 680,000 people, which last year embarked on the long process of membership talks with the EU.
"Not at any price will we allow them to take away our victory, nor will we recognize any institution that accepts a Vujanovic victory," Lekic's Democratic Front, the country's main opposition bloc, said in a statement.
It said it would freeze participation in all parliamentary working groups, a possible prelude to a full boycott of the assembly.
With no independent exit poll or word from electoral authorities, both Vujanovic and Lekic took to the airwaves after polls closed on Sunday to pronounce victory, based on their own vote counts.
Vujanovic said he had won 51.3 percent to Lekic's 48.7. The opposition said the victory was Lekic's with 50.5 percent to Vujanovic's 49.5. Lekic compared Vujanovic's victory claim to a "coup d'etat".
Whoever is declared the winner, the closeness of the race serves as a warning to the ruling Democratic Party of Socialists (DPS), which has dominated Montenegro since federal Yugoslavia's early 1990s breakup and steered the country to independence in 2006.
The president is largely a figurehead, with real power vested in the prime minister, DPS leader Milo Djukanovic.
Analysts say an economic slump triggered by falling foreign investment, and persistent allegations of cronyism and corruption, have eaten into the DPS support.
The party won re-election in a parliamentary election in October last year, but without an outright majority.
(Writing by Matt Robinson; Editing by Mark Heinrich)