Pakistan’s anti-corruption agency arrested former Prime Minister Shahid Khaqan Abbasi on Thursday, drawing a furious response from opposition parties, which accused the government of trying to silence its opponents.

The National Accountability Bureau said in a statement Abbasi had been arrested in a case that was opened last year over a liquefied natural gas (LNG) terminal project.

The arrest, as Abbasi was on his way to a news conference in the eastern city of Lahore, adds to a political scene already thick with accusations of corruption and abuse of office with opposition parties planning a day of protest next week.

“I believe today is yet another black day in Pakistan’s history,” Ahsan Iqbal, a senior parliamentarian from Abbasi’s Pakistan Muslim League-Nawaz (PML-N) party, told reporters, accusing Prime Minister Imran Khan of trying to suppress opposition.

“We are not afraid of your fascist acts. Don’t think that you will gag our voices through such arrests,” he said.

Bilawal Bhutto Zardari, the head of the Pakistan People’s Party (PPP), the other main opposition party, condemned Abbasi’s arrest which he said was part of a government “witchhunt” against elected representatives.

The PML-N was already engaged in a bitter standoff with Khan’s government, which came to power last year accusing Abbasi and his predecessor, Nawaz Sharif, of large-scale corruption and mismanagement of the economy.

Sharif was disqualified by the Supreme Court in 2017 over accusations that eventually led to a seven-year jail sentence for receiving undeclared income. Abbasi took over as premier and served for less than a year before losing an election to Khan’s Pakistan Tehreek-e-Insaf (PTI) party in 2018.

The PML-N accuses the government of being behind Sharif’s arrest and last week produced video footage that it said showed the judge who heard the case confessing that he had been blackmailed to ensure a conviction.

The judge denied the accusation but was sacked from his position with the Accountability Court.