TUNIS (Reuters) - Tunisia's public prosecutor extended on Monday the detention of two journalists, while lawyers began a one-day strike to protest against the arrest of a prominent critic of the president, amid a growing political crisis in the country.

Tunisian police stormed the building of the deanship of lawyers on Saturday and arrested Sonia Dahmani, a lawyer known for her fierce criticism of President Kais Saied.

In a separate incident on the same day, two IFM radio journalists, Mourad Zghidi and Borhen Bsaiss, were also arrested over radio comments and social media posts, according their lawyers.

The spokesman for the public prosecutor, Mohamed Zitouna, said that the detention of both Zghidi and Bsaiss was for a crime related to defamation, without giving details.

Dozens of lawyers gathered on Monday in front of the courtroom, where a judge was expected to begin hearing Dahmani's case, chanting slogans including: "What a shame, the lawyers and the judiciary are under siege."

The public prosecutor's spokesman said the case against Dahmani had nothing to do with her practice as a lawyer, without giving further details.

Dahmani was arrested after she said on a television programme last week that Tunisia was a country where life was not pleasant. She was commenting on a speech by Saied, who said there was a conspiracy to push thousands of undocumented migrants from Sub-Saharan countries to stay in Tunisia.

On Sunday, hundreds of protesters gathered in the Tunisian capital to demand the release of imprisoned journalists, activists and opposition figures, and the setting of a date for a fair presidential election.

Saied took office following free elections in 2019, but two years later seized additional powers when he shut down the elected parliament and moved to rule by decree.

He also assumed authority over the judiciary, a step that the opposition called a coup.

Saied rejects the accusations and says that his steps are legal and aim to end years of chaos and corruption and begin holding all those involved accountable, regardless of their positions or political affiliations.

The latest protests comes amid an economic and political crisis and a wave of arrests targeting journalists, lawyers, activists and opponents.

Most opposition leaders have also been in prison for months, including Abir Moussa, leader of the Free Constitutional Party, and Rached Ghannouchi, the head of Islamist Ennahdha Party, on various charges, in addition to other leaders accused of conspiring against state security.

"Lawyers and journalists are pillars of freedom and they face ongoing restrictions now. Journalists and lawyers are being tried today only for their opinions," said Amira Mohamed, an official at the National Journalists Syndicate said.

(Reporting By Tunisia newsroom; Editing by Alex Richardson)