Updated November 29, 2am

Protesters including two of Daphne Caruana Galizia's sons angrily waited for ministers to emerge from an urgent Cabinet meeting that stretched into the night on Thursday, in response to the news that former chief of staff Keith Schembri has been released from police custody.

"It's an information blackout," Matthew Caruana Galizia told the press in the early hours of Friday morning, as his brother Paul stood beside him.

"We know nothing. The family knows nothing, journalists know nothing, people know nothing. That's why we're here".

Ministers entered the Prime Minister's office at Castille at 8.30pm. They were still inside at 2am.

Police erected barricades as protesters held placards reading, among others, 'Żibel' (rubbish), 'Murderers' and 'Xbajt' (I’m fed up).

"How on earth can we live with ourselves as citizens of this country while those criminals are still governing us, keeping us here in this metal cage?" Mr Caruana Galizia asked in frustration.

At one stage, tensions rose in the crowd after police and protesters pushed against each other. The situation quickly calmed down.

Civil society organisations have called another protest on Friday at 6pm in the wake of the Daphne Caruana Galizia murder probe.

In a statement, civil society groups Repubblika and Occupy Justice and blogger Manuel Delia described Mr Schembri's release as "an attack on Maltese democracy and justice".

The Prime Minister, they said, exercised his "disproportionate powers" to protect "his best friend if not himself as well" from paying for crimes.

Keith Schembri’s release was incomprehensible, they said.

Mr Schembri, who served as the Prime Minister's chief of staff until Monday night, was taken into police custody the following morning.

Murder mastermind suspect Yorgen Fenech has claimed Mr Schembri was behind the murder. He is seeking a Presidential pardon to reveal all on Mr Schembri and former ministers Chris Cardona and Konrad Mizzi. He submitted an official request on Saturday and another to President George Vella on Thursday.

Dr Mizzi has resigned from his post while Dr Cardona has suspended himself.

The organisations accused the Prime Minister of protecting the people and said Joseph Muscat should have resigned to allow justice to run its course.

Malta no longer had an effectively functioning democracy but a Prime minister who ruled by decree and allowed his friends to steal and kill with impunity, they said.

"We will not take this cowardly outrage lying down and we will say so most clearly so the world can know that not all Maltese people are corrupt, robbers and murders," they said.