Martine Moise, the wife of Haiti's assassinated president who was injured in attack at their private home, has returned to the Caribbean nation following her release from a Miami hospital.

Her arrival was unannounced and surprised many in the country of more than 11 million people still reeling from the killing of Jovenel Moise in a raid authorities say involved Haitians, Haitian-Americans and former Colombian soldiers.

Mrs Moise disembarked the flight at the Port-au-Prince airport wearing a black dress, a black bulletproof jacket, a black face mask, and her right arm in a black sling.

She was greeted by Interim Prime Minister Claude Joseph and other officials.

Earlier this week, she tweeted from the Miami hospital that she could not believe her husband was gone "without saying a last word", adding: "This pain will never pass."

On Friday, government officials had announced that Mr Moise's funeral would be held on July 23 in the northern Haitian city of Cap-Haitien and that his wife is expected to attend.

She arrived hours after a key group of international diplomats appeared to snub the man currently running Haiti by urging another politician, the designated prime minister, to form a government following Mr Moise's killing.

Mr Joseph has been leading Haiti with the backing of police and the military despite the fact that Mr Moise had announced his replacement a day before the president was killed on July 7.

Mr Joseph and his allies argue that the designated successor, Ariel Henry, was never sworn in, though he pledged to work with him and with Joseph Lambert, the head of Haiti's inactive Senate.

The statement was issued by the Core Group, which is composed of ambassadors from Germany, Brazil, Canada, Spain, the US, France, the European Union and representatives from the United Nations and the Organisation of American States.