Malta's government has offered an "unprecedented" 1 million euros ($1.18 million) reward, and safety guarantees, for anyone who can provide information about who murdered a high-profile journalist and blogger earlier in the week.

Daphne Caruana Galizia, 53, an investigative journalist whose corruption stories took aim at Prime Minister Joseph Muscat and other top government officials, was killed by a car bomb a short distance from her home on Monday.

The reward offer included a government statement calling her murder a "case of extraordinary importance."

It called the reward offer an "unprecedented measure," and said it was offering the sum to "whoever comes forward with information leading to the identification of those responsible" for her slaying.

"The government is fully committed to solving the murder ... and bringing those responsible to justice," the statement said.

Several years ago the government offered a reward for information about a bank robbery, but this is believed to be the first time it has offered a reward in a murder case.

There have been 15 mafia-style bombings or comparable attacks in Malta over the past decade, but many of the cases remain unresolved.

Leading European Union officials denounced Caruana Galizia's murder as an attack on the free press, and insisted that the rule of law prevail in the Mediterranean island nation.

Link to Panama Papers scandal

Malta is a well-known tax haven and a tempting venue for those looking to launder or hide ill-gotten funds.

Caruana Galizia's murder shocked the island's inhabitants, many of whom eagerly followed her blog posts on corruption to see which business, financial or political figures were in her crosshairs.

The government had asked Caruana Galizia's family to support their reward effort, but there was no immediate comment from her husband and three sons, one of whom is also an investigative reporter, on Saturday.

But earlier in the week they rejected Prime Minister Muscat's request for their "endorsement" of the government's reward offer, and called on him to resign.

"This is how he can get (our endorsement): show political responsibility and resign ... for failing to uphold our fundamental freedoms" to the point where their mother "no longer felt safe walking down the street," they said.

They also called on the government to fire the country's top police commissioner and the attorney-general so "then we won't need a million-euro reward and our mother wouldn't have died in vain."

Caruana Galizia's reporting revealed Maltese links to the Panama Papers scandal. Her reporting included stories about Muscat's wife, alleging she had an offshore account that was used to move money from high-level Azerbaijan figures. The Muscats denied having such an account and any wrongdoing.

Other top government officials, including a minister and Muscat's chief-of-staff, had filed libel suits against the murdered journalist.

bik/tj (AP, dpa)