Civil society groups which have been leading protests calling for the prime minister to resign immediately have urged supporters to meet in Valletta on Friday morning to mark Republic Day.

"Republic Day belongs to the people" civil society NGOs Repubblika and Occupy Justice and blogger Manuel Delia said in a statement on Wednesday.

"The best way to celebrate Republic Day is to defend the Republic from the web of criminality that has taken hold of our country’s institutions.

"We therefore urge all Maltese and Gozitans of good will to join us in Valletta on Friday 13th December at 9.15am The public is invited to bring posters and whistles to deliver its message clearly," they said.

The NGOs have organised two large demonstrations in Valletta and several smaller ones calling for Joseph Muscat to step down immediately and for all those implicated in the murder of Daphne Caruana Galizia to be investigated.

The last mass protest was on Sunday, when thousands filled Castille square in protest.

Friday's protest could potentially clash with official Republic Day events, including a march down Republic Street by the AFM followed by a parade on the Palace Square. 

The official programme of events shows that the prime minister will not be present and the deputy prime minister will be present instead.

Dr Muscat is due to attend the EU's December summit on Thursday and Friday.