Caruana Galizia, 53, was highlighted by politics website Politico as one of 28 individuals who would have a major impact on Europe in 2017 after her work in exposing corruption within Malta's political scene.
"There are crooks everywhere you look now".
It was through her blog, past year that she unveiled the existence of two Panama companies that belonged to minister Konrad Mizzi and Prime Minister chief of staff Keith Schembri.
Locals said Caruana Galizia had just left her house and was on a road near the village of Bidnija in northern Malta when the bomb detonated, sending her auto flying into an adjacent field.
He announced that the US Federal Bureau of Investigation (FBI) had agreed to help local police investigate the killing and was flying experts to the island as soon as possible.
"I will not rest until justice is done".
Malta is the European Union's smallest state and has a population of 400,000.
"The only remedy for anyone who felt slandered was through the courts".
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I've a lot of respect for him, it's not easy to do what he does. Just go for it, win your battles and anything can happen. He will score goals and we will help him score goals.
The couple denied the allegations, rejecting accusations they had used secret offshore bank accounts to hide payments from the ruling family of Azerbaijan.
She subsequently published stories alleging that Muscat's wife, Michelle, received $1 million from the daughter of Azerbaijan's president through a company set up by the same law firm.
Looking for a vote of confidence to counter the allegations, Muscat called snap elections in June which he easily won.
Ms Caruana Galizia had been sued for libel because of various articles she wrote on her blog Running Commentary, and she had filed a report with police two weeks ago that she was receiving threats. It gave no further information.
Adrian Delia, leader of the opposition Nationalist Party, described the event on Twitter as "the collapse of democracy and freedom of expression".
Wreckage of investigative journalist Daphne Caruana Galizia's vehicle next to a road in the town of Mosta, Malta, October 16, 2017.
Caruana Galizia started to contribute regular columns to The Malta Independent and was well-known for her direct style of writing.