Ariel Henry speaks during his appointment as the new Prime Minister in Port-au-Prince, Haiti, Tuesday, July 20, 2021, weeks after the assassination of President Jovenel Moise at his home. (AP Photo/Matias Delacroix)

PORT-AU-PRINCE, Haiti — Haiti's government installed a new prime minister on Tuesday, while officials mourned assassinated President Jovenel Moïse and arrested at least three police officers implicated in his killing.

Designated Prime Minister Ariel Henry was sworn in to replace interim Prime Minister Claude Joseph, who assumed leadership of Haiti with the backing of police and the military after the July 7 attack at Moïse's private home, which also badly injured his wife and stunned the nation of more than 11 million people.

“The task that awaits us is complex and difficult,” Henry said as he called for unity and promised to meet with various sectors in upcoming days to build consensus. “I'm from a school that believes in dialogue.”

He also thanked “sister nations” that he didn't identify for their solidarity and expertise in the ongoing investigation as he demanded that all those responsible be brought to justice.

Authorities pose for a group photo in front of the portrait of late Haitian President Jovenel Moise at at the National Pantheon Museum during his memorial service in Port-au-Prince, Haiti, Tuesday, July 20, 2021. Moise was assassinated on July 7 at his home. (AP Photo/Joseph Odelyn)

Interim Prime Minister Claude Joseph speaks during a memorial service for late Haitian President Jovenel Moise at the National Pantheon Museum in Port-au-Prince, Haiti, Tuesday, July 20, 2021. Designated Prime Minister Ariel Henry is expected to be sworn in later in the day to replace Joseph, who assumed leadership of Haiti with the backing of police and the military after the July 7 attack at Moïse's private home. (AP Photo/Matias Delacroix)