BRUSSELS, DEC. 14 (MONDAY) -- Prime Minister Wilfried Martens' center-right government lost ground to the Socialists in nationwide elections but held on to a slim parliamentary majority, according to nearly complete returns today.

Based on 94 percent of the vote counted, the coalition of Christian Democrats and Conservatives lost five seats, but held 110 in the 212-member Parliament.

The Interior Ministry said final results were not due until later today.

The elections, which took place yesterday, made the opposition Socialists the largest single political force in Parliament, with 72 seats. This could return it to government after a six-year absence, depending on alliances.

As early returns showed Martens' coalition losing at least five legislative seats, he called the voting a setback for his current austerity plan, a key campaign issue, and blamed political conflict between French- and Dutch-speaking Belgians for his coalition's poor performance at the polls.

"I had not expected the verdict . . . would be as severe as it is. With these statistics, it is not possible to form a stable and coherent government," Martens said on television yesterday.

About 7 million people had been expected to vote in this bilingual nation of 10 million, where balloting is mandatory.

Martens' own Dutch-speaking Christian Democrats lost six seats, for a total of 43. The Francophone Christian Democrats won 19 seats in Parliament, down one, and the Francophone Conservatives won 22 seats, down two. The Dutch-speaking Conservatives were projected to be the sole coalition winner, winning three seats, for a total of 25.

The Francophone Socialist Party was projected to win five seats, for a total of 40. With their Dutch-speaking counterparts remaining unchanged at 32, the Socialists became Belgium's largest political force.

Eleven of the 29 parties in the elections held seats in the previous Parliament. In Belgium, all political parties are split into French-speaking and Dutch-speaking memberships.

Martens, 51, called the elections on Oct. 19, the day his coalition collapsed in a linguistic dispute. Preelection polls had predicted that the four-party coalition, the seventh Martens has headed since 1979, would lose its majority. The polls predicted gains for the Socialists.

The Dutch-speaking Socialists are led by Karel van Miert. The Francophone Socialist party is led by Guy Spitaels.

Whatever coalition emerges from the voting, talks to form a new government, Belgium's 35th since World War II, will be difficult. The next Parliament is to make sweeping changes in the constitution to give more autonomy to Flanders, Belgium's Dutch-speaking northern half, and Wallonia, the French-speaking southern region.

The changes are considered necessary to end bickering between Dutch and French speakers. Since 1980, the two regions have had limited autonomy in regional economic, social and cultural matters.

It was a language dispute -- the refusal of the militant Francophone mayor of a Flemish farming village to speak Dutch as required by law -- that brought down the government Oct. 19.

There are about 5.5 million Dutch-speakers in Belgium and 4.5 million Francophones.