Two hitmen brothers were each sentenced to 40 years in prison Friday for killing a prominent journalist in Malta five years ago, an assassination that sparked an international outcry.

The murder sparked mass protests in Malta and eventually led to the resignation of the prime minister, Joseph Muscat.

The sentences handed down to George and Alfred Degiorgio came on the first day of their trial for the 2017 killing of journalist Daphne Caruana Galizia.

The dramatic proceedings saw them plead not guilty before a judge in the morning, before changing their pleas hours later. 

"Their position has changed... they declare they are guilty," defence lawyer Simon Micallef Stafrace told the court, ahead of the sentencing.

The car bomb killing of 53-year-old investigative journalist Caruana Galizia, described as a "one-woman WikiLeaks", led to widespread anger internationally.

One of Malta's most prominent public figures, Caruana Galizia was a vocal critic of the country's political elite, whom she accused of cronyism and corruption via her blog.

The October 16, 2017 car bomb attack near her home came hours after she had posted a message that read: "There are crooks everywhere you look now. The situation is desperate."

"Today's judgement is another important step towards justice for the Caruana Galizia family," Malta's Prime Minister, Robert Abela, wrote on Twitter.

Still awaiting trial is wealthy Maltese businessman Yorgen Fenech, considered by prosecutors to be the alleged mastermind of the murder.

'Investigate your friends'

The much-delayed trial of the brothers -- charged with homicide, causing a fatal explosion and criminal conspiracy, among other crimes -- began Friday with a dramatic outburst from defendant George Degiorgio 

"Don't you know who killed Daphne?" Degiorgio called to the prosecution upon entering court. 

"Your friends, those you were shoulder to shoulder with... Go investigate them!"

A third hitman, Vincent Muscat, pled guilty last year to the murder and was sentenced to 15 years in jail.

As the trial opened, judge Edwina Grima said a defence request to suspend the trial, due to what lawyers said was their lack of time to prepare, had been refused.

Courtroom observers Friday included representatives from press freedom groups, including Reporters without Borders and the European Centre for Press and Media Freedom.