Haitian police said Monday they had arrested the head of Jovenel Moise's security as part of the ongoing investigation into the president's July 7 assassination.

Security chief Jean Laguel Civil is suspected of involvement in the plot that saw Moise killed at his home in the middle of the night by armed commandos who bypassed the president's guards without firing a shot.

Civil had already been placed in solitary confinement at a prison in Delmas, near Port-au-Prince.

"I can confirm that Jean Laguel Civil was arrested Monday by police as part of the investigation into the assassination of president Jovenel Moise," police spokeswoman Marie Michelle Verrier told AFP.

The casket of slain Haitian president Jovenel Moise at his funeral on July 23, 2021 The casket of slain Haitian president Jovenel Moise at his funeral on July 23, 2021 Photo: AFP / Valerie BAERISWYL

Port-au-Prince commissioner Bed-Ford Claude had already ordered immigration authorities to prohibit four police officers who were responsible for Moise's security from leaving the country.

Police on Monday also issued a warrant for Wendelle Coq Thelot, a judge for the highest court in the country who had been fired by Moise.

Details of the assassination remain unclear, but newly installed Prime Minister Ariel Henry has promised to bring Moise's killers to justice.

Police have arrested some 20 Colombian mercenaries as part of the plot they say was organized by a group of Haitians with foreign ties.