Her revelations that Muscat’s wife and cabinet members had secret offshore accounts prompted snap elections on the island in June. But she had also published fraud allegations against the opposition Nationalist Party.

Muscat, speaking on TV on Monday, said: “Everyone knows Ms Caruana Galizia was a harsh critic of mine, both politically and personally, but nobody can justify this barbaric act in any way”. “Everyone has the right to write and say what they want in this country,” he said.

He vowed to bring her killer to justice and called for national unity, saying: “In these moments, when the country is shocked by such a vicious attack, I call on everyone to measure their words, to not pass judgement and to show solidarity”.

Roberta Metsola, an MEP from the Nationalist Party, called the murder “truly the darkest day for democracy in a generation”.

Shock

Caruana Galizia wrote a hard-hitting blog on politics.

She was also a columnist for The Sunday Times of Malta and The Malta Independent and had contributed articles to EUobserver.

Maltese broadcaster TVM said she had reported a death threat to the police 15 days ago.

In February, a special envoy from the OSCE, a European democracy watchdog, also urged Malta to “ensure that journalists” like her could do their work “without being intimidated or threatened.”

Caruana Galizia leaves behind three children and her husband.

“She herself would never have thought that it could have ended this way,” Matthew Lowell, a political consultant in Malta who knew her socially, told EUobserver.

“She was very strong willed, very determined. She never shied away from speaking her mind, but she was also very caring – the mother of three sons,” Lowell said.

Sensitive case

Lowell, who works for Binda Consulting International, said the partisan nature of Maltese politics meant that only an independent body could handle the crime.

“The Maltese government should have no option but to bring in an independent investigator to look at the case”, he said.

The International Consortium of Investigative Journalists (ICIJ) in Washington, which worked with her son, also paid tribute to her.

It said she “has been at the forefront of important investigations in the public interest and has exposed offshore dealings of prominent political figures in Malta.”

“The ICIJ calls upon the Maltese authorities to investigate the murder and bring the perpetrators to justice,” it said.