Prague - Preliminary results showed Czech Prime Minister Mirek Topolanek's party losing the Senate run-off elections Saturday, a crucial electoral test ahead of his country's EU presidency in the first half of next year.

As the last votes were being counted, the candidates for Topolanek's Civic Democrats were shown losing in all but three races. The party needs to defend nine seats to retain their absolute majority of 41 in the 81-seat upper house.

Topolanek's arch-rivals, the main opposition Social Democrats, were leading in 22 races, while a Communist candidate won one.

Voters were choosing 26 senators. One Senate race was already decisively won by a Social Democratic candidate in the first round of voting last week.

The poor result for the Civic Democrats, just a week after they lost a regional election, was expected to further weaken the premier.

His opponents within the party, led by Prague mayor Pavel Bem and backed by President Vaclav Klaus, may seize the moment to replace him at the party's helm at a party congress in December.

"I will have to decide whether I will run and defend the post of the (party) leader at the congress," Topolanek said on Czech television.

He said that voters were punishing his government for the pro- market belt-tightening reforms, such as direct fees for medical care.

"Although the government has ruled well, its image in the society was not such," he said. "(Governments) pay for reforms everywhere in the world."

Meanwhile, Social Democratic leader Jiri Paroubek described as "an epochal success" the anticipated final results, which would mark his party's first victory in a Senate election since it came to existence in 1996. dpa