The sons of murdered investigative journalist Daphne Caruana Galizia are calling for the Maltese prime minister's resignation, saying he should show political responsibility for "failing to uphold our fundamental freedoms".
The sons wrote on Facebook that they refused to endorse Joseph Muscat's call for a reward to lead to their mother's assassins, saying: "We are not interested in justice without change."
Ms Caruana Galizia, a harsh critic of Mr Muscat who reported extensively on corruption on the island nation, was killed by a car bomb on Monday.
Her sons wrote that identifying their mother's assassins is not enough, and corruption on the Mediterranean island nation also needs to be rooted out.
The sons said: "We are not interested in a criminal conviction, only for the people in government who stood to gain from our mother's murder to turn around and say that justice has been served."
Investigators are looking at similarities with five other car bombings in Malta over the last two years, none of which have been solved.
Police commissioner John Rizzo told the Malta Independent it appears that mobile-detonated explosives were used in each of the six bombings since the start of 2016, which caused four deaths and two serious injuries.
The previous victims were all known to police, the paper said.
"Very few people could construct such a bomb. Instructions may be obtained online but building such a device would still require a certain degree of skill," Mr Rizzo said.
Investigators have not publicly identified which explosives were used in the journalist's murder, but experts say military grade explosives like Semtex are not available in Malta and would have to be brought in from abroad.
Mr Muscat defended the failure to solve the rash of car bombings as he left parliament on Wednesday evening.
"I will continue to defend the institutions and I am a firm believer in the institutions," he said.