LUSAKA (Reuters) - Zambian President Edgar Lungu on Monday defended the tax collection agency's decision to shut down a newspaper critical of the government, saying the revenue service did so to recoup unpaid taxes.

The Zambia Revenue Authority (ZRA) shut down the Post newspaper last week, demanding $6 million in unpaid taxes.

But the newspaper's managing editor Joan Chirwa accused the ZRA of trying to silence it head of general elections in August, and claimed that the outstanding bill was in dispute.

The tax authority was not available to comment on Chirwa's claims or whether there was a tax dispute.

"The decision by the Zambia Revenue Authority to take over assets of the Post newspaper was indeed an independent action to recover tax debt," Lungu said an address to his diplomats.

"Some of you are saying that the timing of the court's decision is awkward. Tell me when is the right time to do this?"

The European Union delegation and the heads of mission of the EU member states last week said in a statement that they were concerned by the closure of the newspaper.

The action comes seven weeks before the August 11 amid campaigning for the presidential and parliamentary polls.

Police in April briefly detained two journalists who work at the Post over a story quoting an opposition leader as saying that Lungu had used public funds to pay for a holiday. The president has denied the report.

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. Lungu faces a strong challenge from opposition leader Hakainde Hichilema of the United Party for National Development at the polls.

Hichilema accused the government in an interview with Reuters on Thursday of using repressive laws to restrict his side's campaigns, citing the closure of the Post, but Presidential spokesman Amos Chanda denied the accusations, saying that the opposition was campaigning freely.

(Reporting by Chris Mfula; Editing by James Macharia)