UPDATE 1-Polish opposition follows government in challenging Senate results

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WARSAW, Oct 22 (Reuters) - Poland's opposition challenged results in three districts in elections for parliament's upper house on Tuesday, setting the scene for a dispute over a tight result a day after the ruling party submitted requests for recounts in other districts.

Poland's governing Law and Justice (PiS) party retained a majority in Poland's lower house after the Oct. 13 elections, but narrowly lost it in the Senate. The party has asked the Supreme Court to approve recounts in six electoral districts.

The loss of the Senate majority coupled with a smaller than hoped for majority in the lower house came as a blow to PiS, which had hoped for a stronger mandate to continue its overhauls of the justice system, media and cultural institutions.

Opposition parties hold 48 of 100 seats in the upper house, but wield a majority thanks to three independent senators who are broadly supportive.

Polish media have reported that PiS, which also holds 48 upper house seats, has made overtures to opposition senators in an attempt to establish a working majority.

The opposition was requesting either a recount with votes deemed invalid allocated to them or a re-run of the votes in those districts, with the Supreme Court to decide on the course of action, Civic Platform spokesman Jan Grabiec said.

"Our protests would take place regardless of whether or not PiS submitted theirs. We have real grounds for our protests," Marek Borowski, a senator from the opposition Civic Coalition grouping which includes Civic Platform, told reporters.

Opposition protests centred around the allegedly mistaken use or confusing positioning of logos on ballot papers, as well as that PiS did not announce early enough its replacement for a candidate who had died.

In a separate news conference, Civic Coalition leader Grzegorz Schetyna questioned the government's motives for demanding the recounts.

"Filing protests, if there is reason to do so, is always justified. If the reason is just losing the election and not accepting the result, such things are fundamentally politically unjust," Schetyna said.

Schetyna added he had received a promise that the Organization for Security and Co-operation in Europe (OSCE) would monitor any recount.

The Supreme Court has up to 90 days to rule on the validity of elections.

"We have nothing to hide, if somebody wants international checks we have nothing against that," PiS deputy spokesman Radoslaw Fogiel was quoted saying by state-run news agency PAP. (Reporting by Alan Charlish, Pawel Florkiewicz and Anna Wlodarczak-Semczukl, Editing by David Holmes and Ed Osmond)