Earlier this week, two government ministers resigned over alleged financial ties to a wealthy businessman charged with involvement in the murder. Mr Muscat had prompted anger by resisting calls for them to be dismissed.
He stepped down just 24 hours after the businessman, Yorgen Fenech, wascharged with being complicitin Ms Caruana Galizia’s murder.
In a televised message on Sunday night, Mr Muscat said he had informed the nation’s president that he would quit as leader of the governing Labour party on 12 January and that in the days after he would resign as prime minister.
His former chief of staff, Keith Schembri, one of those who resigned and had been arrested for questioning in the investigation, was among government members targeted by the journalist’s investigative reporting.
He was released after questioning and denies wrongdoing.
Participants in the street protest carried photos of Ms Caruana Galizia, as well as placards with the last words she wrote on her blog.
“The situation is desperate,” she had written, referring to what she unearthed with her digging into suspected widespread corruption in political and business circles.
On the placards, protesters added the word “still” before “desperate”.
Affixed to the gate outside the courthouse were copies of a photo that was published on Saturday by Malta Todayshowing Ms Schembri with the alleged middleman in the case, taxi driver Melvin Theuma. It was unclear where and when the photo was taken.