Vitoria/Santiago de Compostela, Spain  - A mainstream Spanish party defending the country's unity could oust Basque nationalists from power for the first time in 30 years, preliminary results showed after Sunday's regional elections.

Basque Prime Minister Juan Jose Ibarretxe's Basque Nationalist Party (PNV) won the elections, taking 30 seats in the 75-member regional parliament.

However, Spanish Prime Minister Jose Luis Rodriguez Zapatero's socialists increased their support from 18 to 24 seats.

That would give the socialists an absolute majority if they managed to negotiate a coalition with the conservative People's Party (PP), which took 13 seats, and the tiny Union, Progress and Democracy (UPyD), which won one seat.

Basque socialist leader Patxi Lopez said he felt he had been given the authority to "lead change in the Basque Country."

The PNV, which seeks looser ties to Madrid, has governed the northern region since it was granted a broad autonomy in 1979.

The elections were the first major political test for Zapatero since March 2008, when he won his second mandate. Spain has since slipped into recession at the end of 2008.

Elections were also held in north-western Galicia, where the conservative People's Party (PP) took an absolute majority of 39 seats in the 75-member parliament.

The socialists and Galician nationalists, who had governed in coalition since 2005, took 24 and 12 seats, respectively.

PP leader Mariano Rajoy badly needed a victory in Galicia at a time when his leadership was being questioned after his two successive election defeats to Zapatero and over corruption allegations against the party.

Around 4 million voters were eligible to elect regional parliaments for the Basque region, which has 2.1 million residents, and Galicia, with 2.8 million people.

The Basque elections were the first without the participation of radical separatists close to the militant group ETA, after the formations D3M and Askatasuna were banned on grounds of ETA links.

ETA, which is listed as a terrorist organization by the European Union and the United States, has killed more than 820 people since 1968.

Radicals, who regarded the elections as undemocratic, booed mainstream candidates, and police detained several people for trying to introduce D3M ballots into polling stations.

The night before the elections, police seized materials for making explosives and detained an ETA suspect on charges of planning an imminent attack.

ETA had previously staged two bombings, apparently to protest the bans on D3M and Askatasuna, without causing injuries.

Pro-ETA parties could have been expected to take about 12 per cent of the Basque vote.

The PNV focused its electoral campaign partly on warning Basque voters that a socialist victory would lead to Basque affairs being managed from Madrid.

The socialists had increased their support after Zapatero made an attempt to negotiate with ETA in 2006.

The incipient talks collapsed after six months, but the premier was seen as having made a serious attempt to seek a political solution to the Basque conflict.

Lopez claimed to be able to unite the Basques, who are divided over independence.

The PNV is also internally divided over the radical policies of Ibarretxe, whose attempts to stage a regional vote on Basque self- determination were blocked by the Spanish Parliament and judiciary.

In Galicia, where the issue of self-determination played a lesser role, socialist chances were seen as having been undermined by accusations of wasteful management and by Spain's deepening recession.

Rajoy, himself a Galician, had campaigned extensively in the region, which is a traditional conservative stronghold.

A judge is currently investigating about 40 people over allegations that PP-governed municipalities granted contracts worth tens of millions of euros and issued illegal building permits in exchange for bribes.

The PP accused Justice Minister Mariano Fernandez Bermejo of trying to influence the probe, after he was found to have gone on a hunting trip with the investigating judge. Bermejo resigned over the affair, six days before the regional elections.

The Galician elections aroused considerable interest in Latin America, which has numerous residents of Galician origin.

Eligible voters included 335,000 Galicians living outside Spain. The countries with most Galicians include Argentina, Venezuela, Brazil, Uruguay, Mexico and Cuba. (dpa)