VALLETTA, Malta — Destabilized by a widening investigation into the 2017 murder of Malta’s best-known journalist, the prime minister of the Mediterranean island nation announced on Sunday that he would resign, but not leave office until January, following an uproar over the possible role of close associates in the killing.
The announcement by Prime Minister Joseph Muscat came just a few hours after thousands of protesters gathered in the Maltese capital, Valletta, to demand his immediate resignation. It was the largest in a series of demonstrations in recent days triggered by suspicions that senior officials knew in advance about the plot to kill the journalist, Daphne Caruana Galizia, and later tried to cover it up.
The protesters, chanting “assassins, assassins” and “shame on you,” marched along the ancient capital city’s main shopping street to the courthouse where, on Saturday, a prominent local businessman, Yorgen Fenech, was arraigned on charges of complicity in the murder of the journalist and other crimes related to the killing.
Ms. Caruana Galizia, who was loved by some and loathed by others for her reporting — a mix of real scoops and scabrous, personal attacks — was killed in October 2017 by a bomb planted in her car that, detonated by a cellphone, exploded as she was driving away from her family’s home.
A previously slow-moving investigation into the murder suddenly accelerated last week and reached the upper levels of the government. Mr. Muscat’s chief of staff, Keith Schembri, an old friend of the businessman charged on Saturday, resigned on Tuesday. He was taken in for questioning by investigators looking into the murder but was later released.
Mr. Muscat’s tourism minister, Konrad Mizzi, also resigned, and the economy minister, Christian Cardona, said he was suspending his duties until the murder investigation ended.
All three men had come under withering criticism and personal attack from Ms. Caruana Galizia before she was killed. Mr. Schembri and Mr. Mizzi owned offshore companies set up to receive money from a mysterious company known as 17 Black that had been registered in the name of Mr. Fenech, the businessman and prime suspect in the murder case.
Prime Minister Muscat, in a televised address to the nation Sunday evening, said he was sorry for his mistakes, acknowledging, “I am not perfect.” But said he would delay his departure “to ensure stability.”
Simon Busuttil, a former leader of the opposition who took part in Saturday’s protest, said Mr. Muscat’s announcement that he would leave office after his governing Labour Party selected a new leader on Jan. 12 was “not enough.”
“He must go now,” he added.
At the protest, Eve Borg Bonello, a teenage anti-government activist who spoke at the protest rally earlier, drew uproarious applause when she shouted: “Joseph, your time is up now.” Many waved photographs of the murdered journalist or signs paying tribute to her work exposing corruption. “Daphne, you were right!” said one.