* BGK bought 512 million rights for 2.71 zlotys each
* Sale to help Poland's state budget
* Rights subscription deadline next week
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WARSAW, Oct 15 (Reuters) - Poland's state bank BGK bought 512 million rights to buy shares in the country's top bank PKO BP from the government for 1.39 billion zlotys ($492.9 million), BGK chief executive told Reuters on Thursday.
Thursday is the last day to trade the instruments, four of which give the right to buy one new share in PKO's 5 billion zlotys cash call, Poland's largest issue since the bank's initial public offer in 2004.
"I confirm we bought the rights for 2.71 zlotys each," Ireneusz Fafara said.
The inflows from the sale of its rights will help Poland keep down its stretched state budget, which will also receive a boost from an expected extraordinary dividend expected to be paid out by PKO following the share issue.
Poland, which has 52 percent of PKO, will retain indirect control of the bank following the cash call.
Other shareholders have the right to subscribe for the new rights through Tuesday.
Shares in PKO were flat at 33.21 zlotys by 1026 GMT, in line with the directionless market. (Reporting by Marcin Goettig, writing by Chris Borowski; Editing by David Cowell)