KINGSTON, Jamaica, March 11 (Reuters) - Haiti's unelected prime minister, Ariel Henry, will step down once a transition council and temporary replacement have been appointed, he said on Monday, after leading the Caribbean country since the 2021 assassination of its last president.

Armed gangs massively grew their wealth, influence and territory under his administration, prompting Henry to travel to Kenya in late February to secure its support for a United Nations-backed security mission to help police.

However, the conflict dramatically escalated in his absence and left the 74-year-old neurosurgeon stranded in the U.S. territory of Puerto Rico while regional leaders called for a swift transition.

"The government that I am leading will resign immediately after the installation of (a transition) council," Henry said in a video address. "I want to thank the Haitian people for the opportunity I had been granted."

"I'm asking all Haitians to remain calm and do everything they can for peace and stability to come back as fast as possible," he added.

Videos distributed on Haitian social media appeared to celebrations in the street, with people dancing to music in a party atmosphere and fireworks launched into the night sky.

A senior U.S. official said Henry was free to remain in Puerto Rico or travel elsewhere, though security in Haiti would need to improve for him to feel comfortable returning home. The official said the resignation had been decided on Friday.

Photo from Reuters