LUSAKA (Reuters) - Zambian police on Tuesday charged three people including two editors of a newspaper critical of the government that was shut down last week, as tensions rose in the run up to elections in August.

The Zambia Revenue Authority (ZRA) shut down the Post newspaper last week, demanding $6 million in unpaid taxes but the newspaper accused the authorities of trying to silence it, and claimed the outstanding bill was part of a court dispute.

Tax officials have not commented on the matter, but Zambian President Edgar Lungu on Monday defended the ZRA's action, saying it did so to recoup unpaid taxes.

On Tuesday, the Post's managing editor Joan Chirwa said police arrested its editor-in-chief Fred Mmembe, his wife Mutinta and deputy managing editor Joseph Mwenda late on Monday.

"This was after the trio gained entry into the Post newspaper's head office in Rhodespark following a stay granted by the court restraining ZRA from seizing the newspaper's property," Chirwa told Reuters.

She said the Post - which has continued publishing from an unknown location - obtained a court order to resume operations but the police said it had not been signed by ZRA.

Police spokesman Rae Hamoonga said the three had been charged and released on bond and will appear in court next week to face charges of, among others, breaking into a building.

The opposition says the government was using repressive laws to restrict its campaigns and that there was a media clamp down. The presidency has denied the claims, saying the opposition was campaigning freely.

Lungu has been in power for just over a year after winning a ballot triggered by the death of his predecessor, Michael Sata, in October 2014. He faces a strong challenge from opposition leader Hakainde Hichilema of the United Party for National Development at the polls.

(Reporting by Chris Mfula; Editing by James Macharia)