TUNIS (Reuters) - A senior official in Tunisia's main opposition Ennahda party told Reuters it planned to go ahead with a protest against President Kais Saied on Friday in defiance of a new COVID-19 ban on gatherings.

       The government said earlier it was re-imposing a night curfew, banning all gatherings for two weeks and discouraging people from travelling abroad to stop the rapid spread of COVID-19 cases.

       Ennahda and other parties accuse the government of using the rules to stop protests against Saied, who in July sacked the prime minister, suspended parliament and assumed broad powers in moves they call a coup.

       They had planned a major protest on Friday against Saied in central Tunis, but any public demonstration would be in breach of the new rules.

       "In principle, Ennahda will go ahead with the Friday protest," said the official, Mohamed Goumani.

       The moderate Islamist Ennahda was the largest party in the suspended parliament with about a quarter of seats and had played a role in successive coalition governments since the 2011 revolution that introduced democracy.

       Saied, who insists his actions were necessary to save the state and denies harbouring dictatorial ambitions, has started rewriting the country's constitution and says he will put it to a referendum this summer before a new parliament is elected.

       "The decision (to ban gatherings) is a political one, not a scientific one, especially given that hundreds of thousands of students will be going to school," Goumani added.

       The previous government's perceived poor response to the pandemic, including a botched vaccine roll-out, raised the political pressure before Saied's intervention in July.

       Leaders of two other parties that had joined the call for protests on Friday also accused the government of restoring the health restrictions for political reasons.

       "We will be on Revolution Street to protest whatever the cost," Ghazi Chaouachi, the head of Attayar, which had 22 of the suspended parliament's 217 seats, told reporters, using a nickname to describe the capital's Habib Bourguiba Avenue.

       The measures were intended "to prevent a wave of popular anger that they can only confront by citing health conditions", said the leader of the smaller Joumhouri Party, Issam Chebbi.

       (Reporting by Tarek Amara, writing by Angus McDowall; Editing by Jon Boyle and Alex Richardson)