The trial of two brothers charged in the car-bomb assassination of a Maltese journalist who investigated corruption in the tiny island nation is under way, nearly five years after the killing sent shockwaves across Europe.

George Degiorgio, 59, and Alfred Degiorgio, 57, are charged with having set the bomb that blew up Daphne Caruana Galizia’s car as she drove near her home on October 16 2017.

Prosecutors allege they were hired by a top Maltese businessman with government ties. That businessman has been charged and will be tried separately.

The Degiorgio brothers have denied the charges. A third suspect, Vincent Muscat, had earlier changed his plea to guilty. Muscat is currently serving a 15-year sentence.

In a Valletta courtroom on Friday, Alfred Degiorgio pleaded not guilty while his brother declared that he had nothing to say. The court interpreted that as a not guilty plea.

George Degiorgio has promised to implicate others in the plot to assassinate Caruana Galizia.

The brothers had unsuccessfully tried to negotiate a pardon in exchange for naming bigger alleged conspirators, including a minister whose identity has not been revealed.

The bomb had been placed under the driver’s seat and the explosion was powerful enough to send the car’s wreckage flying over a wall and onto a field.

A top Maltese investigative journalist, Ms Caruana Galizia, 53, had written extensively on her website “Running Commentary” about suspected corruption in political and business circles in the Mediterranean island nation, an attractive financial haven.

Among her targets were people in then-Prime Minister Joseph Muscat’s inner circle whom she accused of having offshore accounts in tax havens disclosed in the Panama Papers leak. She also targeted the opposition, and she was often sued by those she wrote about.

Two weeks before her death, she had filed a police report saying she was receiving threats, according to news reports at the time.

The arrest of a top businessman with connections to top government officials two years after the murder sparked a series of mass protests in the country, forcing Mr Muscat to resign.

Yorgen Fenech was indicted in 2019 for alleged complicity in the killing, by either ordering or instigating the commission of the crime, inciting another to commit the crime or by promising to give a reward after the fact.

He was also indicted for conspiracy to commit murder. Fenech has denied all charges.

No date has been set for his trial.

A self-confessed middleman, taxi driver Melvin Theuma, was granted a presidential pardon in 2019 in exchange for testimony against Fenech and the other alleged plotters.

Two men, Jamie Vella and Robert Agius, have been charged with supplying the bomb, but their trial has not yet begun.

A 2021 public inquiry report found that the Maltese state “has to bear responsibility” for Ms Caruana Galizia’s murder because of the culture of impunity that emanated from the highest levels of government.

The Council of Europe’s commissioner for human rights, Dunja Mijatovic, has decried the “lack of effective results in establishing accountability five years later”.

In a letter to the current Prime Minister, Robert Abela, the commissioner expressed the need for urgency in protecting journalists in Malta and cited ongoing defamation cases against Ms Caruana-Galizia’s family.