Three men were charged Tuesday with the murder of campaigning Maltese journalist and blogger Daphne Caruana Galizia, killed in a horrific auto bombing on the Mediterranean island on October 16.
Joseph Muscat said they were all Maltese citizens and were arrested yesterday in a joint operation involving police, army and security services.
They are expected to be arraigned in the coming hours, but so far no official time has been given.
"On Monday, her family reacted angrily to how the arrests were announced - saying police should have informed the family, not Muscat first - and reiterating in a statement their uncertainty if justice will be carried out, despite the prime minister's public insistence earlier in the day that all would be done to solve the case".
Galizia was following leads from the Panama Papers, which were leaked in 2015 and show how the world's rich use offshore firms to hide their wealth.
Just before her death, Caruana Galizia, 53, had posted on her closely followed blog, Running Commentary, that there were "crooks everywhere" in Malta. Authorities did not release the names of any of the 10 suspects.
Olivier Giroud warned that he must leave in January
He has featured more often in the Europa League and Carabao Cup this season, scoring five goals across all competitions. Everton had expressed their desire to bring Giroud to Meyerside, only for the player to turn them down.
The family have raised other concerns about the investigation, which they say appears to be focusing only on forensic evidence rather than examining financial transactions that could uncover vital evidence.
Muscat's Labour Party government had offered a one million euro ($1.2 million) reward for information leading to a conviction of Caruana Galizia's killers. Caruana Galizia wrote about some of those linked to the inquiry.
Caruana Galizia focused her reporting for years on investigating political corruption and scandals, and reported on Maltese mobsters and drug trafficking.
Antonio Di Pietro, an Italian politician and judge who was a prosecutor in Italy's anti-corruption Mani Pulite corruption trials in the 1990s, said on Monday that Caruana Galizia's murder had all the hallmarks of a mafia-style killing.
Responding to a public letter from eight of the world's largest media organisations including the New York Times, BBC and the Guardian, the first vice-president of the European Union commission, Frans Timmermans, last month issued a strong warning to Malta. They also are Maltese, Home Minister Michael Farrugia said.