Maltese Prime Minister Joseph Muscat announced Sunday that he would step down next month, after the investigation into the 2017 killing of an anti-corruption journalist raised questions about the role of his former chief of staff and ensnared other members of the country’s elite.

“This is what the country needs at the moment,” Muscat said in a nationally televised address. He said he would resign as leader of his own party on Jan. 12 and step down as prime minister of the Mediterranean island nation of half a million people in “the days after.”

The decision was the largest political convulsion yet in the investigation into the car bomb death of Daphne Caruana Galizia, a widely read investigative journalist who focused on the corruption of Maltese politicians and other power brokers.

Malta, the smallest member of the European Union, has never faced a comparable political crisis. The full story of how Caruana Galizia’s killing was orchestrated remains unclear, but protesters in recent days had called for Muscat’s resignation, saying he was presiding over a country where coverup and impunity reigned.

Muscat admitted no personal wrongdoing.

“I understand that for this to happen there is a need for a clear signal of a fresh page, and this signal can be given only by me, as I need to shoulder everyone’s responsibilities, even where I am not involved,” he said, according to the Times of Malta.

Muscat has been prime minister since 2013, presiding over a period of relative prosperity, twice winning runaway elections.

But the nation has come to be dominated by the Caruana Galizia investigation, particularly in recent weeks as it has picked up steam. The central development has been the arrest two weeks ago of a prominent businessman, Yorgen Fenech, who was detained by armed officers on his yacht after what Maltese media described as an attempt to flee the country.

Fenech, who has been charged with complicity in the murder, had requested immunity in exchange for revealing information about Muscat’s former chief of staff and other top government figures. Malta’s government has turned down Fenech’s request.

Some of his information has reportedly been unreliable, but critics said the decision was a way to shield government higher-ups.

Muscat’s chief of staff, Keith Schembri, resigned from his position on Tuesday and was held by police for two days last week before being released. He has denied wrongdoing.

Fenech has been identified by Maltese authorities as the owner of a secretive Dubai company, 17 Black. According to a report on the journalist’s killing by the Council of Europe, 17 Black was expected to make “large monthly payments” to secret Panamanian companies owned by Schembri and a Maltese energy minister.

Caruana Galizia had discovered the alleged people behind those companies as part of her work. In her last post, published on her personal blog just before the car bomb was detonated remotely, she called Schembri a “crook.”

Months after her death, three men were arrested on accusations of planting the car bomb.

Critics said Muscat, a close friend of Schembri, needed to step down immediately for the investigation to have credibility. Reuters reported that Muscat kept Schembri in briefings about the investigation even after Fenech, with links to Schembri, had been identified as a suspect in the murder.

Opposition leader Adrian Delia said his party would not participate in any events at which Muscat is present.

“Justice cannot be served with an illegitimate Prime Minister at the helm,” Delia wrote on Twitter.