Daphne Caruana Galizia, Malta's best-known investigative journalist, was killed this morning when a powerful bomb blew up her car.
Ms Caruana Galizia, 53, ran a hugely popular blog in which she relentlessly highlighted cases of alleged corruption, often involving politicians from Malta.
Police said she was killed as she was driving near the village of Bidnija in northern Malta.
Maltese Prime Minister Joseph Muscat, who faced accusations of wrongdoing by Caruana Galizia earlier this year, denounced her killing, calling it a "barbaric attack on press freedom".
"I will not rest until I see justice done in this case. Our country deserves justice," he said in a televised statement, calling for national unity.
Mr Muscat called early elections in June as a vote of confidence to counter Ms Caruana Galizia's allegations of corruption.
She said documents in a small Malta-based bank showed that Mr Muscat's wife was the beneficial owner of a company in Panama, and that large sums of money had been moved between the company and bank accounts in Azerbaijan.
Both Mr Muscat and his wife denied the accusation and Mr Muscat won reelection.