Economy Minister Chris Cardona has played down being questioned by the police in connection with journalist Daphne Caruana Galizia's assassination. 

"This is not questioning about a murder. It is not an interrogation. It's completely different," Dr Cardona said as he walked towards parliament following a four-hour Labour parliamentary group meeting. 

He said the marathon meeting, during which Labour MPs unanimously voted to back Joseph Muscat as leader, was "lovely". 

Dr Cardona was called in for questioning by police on Saturday morning. A ministry statement said the minister was asked "to provide some clarifications" to investigators. 

He later told Malta Today that the police asked him if he was involved in the murder, and whether he knew "middleman" Melvin Theuma, who has since been granted a pardon in exchange for information. 

The minister told Malta Today that he replied "no" to both questions.

Dr Cardona was a frequent target of Ms Caruana Galizia and was suing her at the time of her murder in October 2017.

On Sunday, police investigators also called in one of Dr Cardona's ministry employees for questioning. 

Asked on Monday if he knows suspect Yorgen Fenech, Dr Cardona said: "Of course I know Mr Fenech, who doesn't?"

Questioned about whether he should hand in his resignation in light of the questions asked to him by the police, Dr Cardona said the institutions had to be left to do their work.