Melvin Theuma, the middleman in Daphne Caruana Galizia’s murder, has been released from hospital after undergoing heart surgery, police say. 

Theuma was hospitalised on Saturday after he was taken ill and reported some chest pains. 

Medical examinations later confirmed that one of his arteries had narrowed and he required a stent.

On Wednesday, police said he had been released from hospital.

It was Theuma's second stint in hospital this summer. The key witness in the Caruana Galizia murder case was previously admitted to Mater Dei Hospital on July 21 after he was found in his Swieqi home with multiple stab wounds to his neck and body. 

He was initially in intensive care but was eventually transferred into the ENT ward, where his condition improved rapidly until he was able to hold conversations unaided.

Police said all signs indicated that the stabbing was self-inflicted and Theuma later wrote notes saying he self-harmed out of remorse for his involvement in the 2017 murder and fear that his testimony was being doubted.

Theuma has since been monitored more closely by police officers “for his own safety”. An officer is understood to be stationed inside his property but Theuma is not on suicide watch.

Caruana Galizia was killed in a car bomb in October 2017 in an attack allegedly carried out by brothers Alfred and George Degiorgio, and Vincent Muscat, who has also sought a pardon in exchange for his evidence.

Businessman Yorgen Fenech stands accused of masterminding the murder and a separate inquiry is being held to establish whether the state could have prevented her killing.