TUNIS (Reuters) -Tunisia's interior ministry on Thursday dismissed accusations by lawyers and a rights group that police officers had tortured a detained attorney who collapsed in court.

The attorney Mahdi Zagrouba - a well known critic of President Kais Saied - was arrested on Monday on suspicion of verbally and physically assaulting a police officer during protests against the arrest of another lawyer, prosecutors said.

Zagrouba appeared in front of an investigating magistrate on Wednesday, told the hearing he had been tortured by officers, then collapsed and was taken to hospital, fellow lawyers and witnesses said.

"He mentioned the names of the policemen who tortured him before he suffered a collapse and coma," lawyer Souad Boker, who was representing Zagrouba, said.

The interior ministry said it strongly denied the accusations.

"We categorically deny that the lawyer was subjected to torture or ill-treatment. It is a scenario to escape responsibility after it was proven that he assaulted a policeman during a protest this week," ministry official Fakher Bouzghaia said.

"All detention centres are equipped with surveillance cameras," Bouzghaia added.

Without referring to the allegations, President Saied said in a statement after a meeting with Minister of Justice Laila Jafel late on Wednesday that the state was responsible for guaranteeing every prisoner the right to treatment that preserves their dignity.

Saied took office after free elections in 2019, but two years later shut down the elected parliament. He has since ruled by decree - a move that he has said is necessary to take on what he calls a corrupt elite. His critics have called it a coup.

Zagrouba, who has criticised the president, was detained by police who stormed the bar association's headquarters on Monday for the second time in two days.

The state TAP news agency quoted another of Zarouba's attorneys, Boubaker Ben Thabet, as saying Zagrouba had been subjected to "systematic torture" during his detention.

Toumi Ben Farhat, another lawyer representing Zagrouba, said his colleague "was subjected to extremely severe torture".

Bassam Trifi, the head of the Tunisian League for Human Rights, said that "Zagrouba was subjected to brutal torture, and I personally witnessed the torture on his body".

The Bar Association said in a statement late on Wednesday that torture deserves criminal prosecution, that it held Ministry of Interior officers responsible, an that it had called for a national strike on Thursday.

A day after Zagrouba's arrest, the European Union said it was concerned about a number of imprisonments of civil society figures, journalists and political activists, and demanded clarifications from Tunisia.

(Reporting By Tunisian newsroom; Editing by Gerry Doyle and Andrew Heavens)