The state funeral in the northern city of Cap-Haitien was intended to foster national unity, but the unrest reflected deep divisions over the July 7 atrocity, in which suspected foreign gunmen walked apparently unchallenged into the Moises' residence and shot the president multiple times, also injuring his wife.
Acrid smoke from piles of burning tires and gutted autos blocking roads outside the compound where the ceremony was held billowed into the service, depositing black ash onto mourners.
Delivering an emotive address that switched between French and Creole, Moise's widow Martine closed the ceremony with a call for justice for her husband, rounding on his critics and pledging to continue his efforts to build a fairer Haiti.
"The struggle isn't over yet," she said, her face nearly hidden under a wide-brimmed black hat, and her bandaged right arm in a sling. "He has already shown us the way. And he will be with us until we get there, even though the journey is long."
Few answers have emerged about who planned the killing, or why.
There were no immediate reports of injuries among protesters or mourners at the funeral. Reuters witnesses smelled gas and heard detonations like gunshots outside the site of the service.
Local media reported a nearby home furnishing store was looted during the disturbances. Lines of people could be seen nearby carrying washing machines and other domestic appliances as the last mourners were exiting the compound.
The U.S. delegation filed out of the makeshift arena hosting the service less than an hour after entering. During the service, dozens of armed security personnel formed protective cordons around officials in the stands.
U.S. National Security Advisor Jake Sullivan said Washington was "deeply concerned" about the situation in Haiti as he announced the U.S. delegation had returned home safely.
"We strongly urge all parties to express themselves peacefully, and call on Haiti's leaders to be clear that their supporters must refrain from violence," he said in a statement.
U.S. President Joe Biden's ambassador to the United Nations, Linda Thomas-Greenfield, led the American delegation. Earlier, as her team arrived in Cap-Haitien, she called on Haiti's new Prime Minister Ariel Henry to create conditions for legislative and presidential elections "as soon as feasible."
"The Haitian people deserve democracy, stability, security, and prosperity," said Thomas-Greenfield on Twitter.
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Trouble flared minutes after a brass band and church choir music formally opened Moise's funeral ceremony.
Punctuated by declamations from supporters who accused authorities of responsibility for Moise's death, the service played out in an atmosphere of tension, and the organizers brought the program to close nearly an hour ahead of schedule.
Angry shouts were sometimes drowned out by loud swells of somber devotional music played on loudspeakers.
Wrought with emotion, Moise's immediate family eulogized the late president as a champion of the poor who had dared to challenge Haiti's dominant political and economic elites.
Arguing the Haitian system was stacked against him from the start, Martine Moise said her husband had been a victim of hate-filled enemies and "corrupt oligarchs."
She stayed with his coffin for more than an hour after it was carried to a canopied mausoleum, laid in a concrete tomb about ten feet (three meters) deep, then covered by iron bars, and sealed with planks of wood, cement and large rocks.
The tomb stood near a mausoleum to Moise's father, who died last year.
Earlier, arriving Haitian officials met with protests, with many directing anger at national police chief Leon Charles.
"Why do you have all this security, where were the police on the day of the president's assassination?" one protester said.
The demonstrations have convulsed Cap-Haitien, his hometown, for three days. Protesters have vented anger over the many questions that remain unanswered over his death.
Some saw in the assassination the continuing hand of foreign powers in the poorest country in the Western Hemisphere, which was the first state in Latin America and the Caribbean to become independent from Europe at the start of the 19th century.
Haitian officials say the attack was carried out by a group that included 26 Colombian former soldiers, at least six of whom had previously received U.S. military training.
The turmoil has pushed Haiti up Biden's foreign policy priorities and on Thursday the U.S. State Department named a special envoy for the country. But Biden has rebuffed a request by Haiti's interim leaders to send troops.
Moise himself faced major protests. A Senate audit accused him of involvement in embezzling over $2 billion of Venezuelan aid, claims he dismissed. He angered opponents by ruling by decree and tabling legislation to expand presidential power.
Gang violence surged on his watch and the economy struggled. But support for him was prominent in his hometown. Banners celebrating Moise festooned buildings along the narrow streets of Cap-Haitien's old town, with proclamations in Creole including "They killed the body, but the dream will never die." Reporting by Dave Graham and Andre Paultre in Cap-Haitien; Writing by Frank Jack Daniel; Additional reporting by Ezequiel Abiu Lopez in Santo Domingo and Michelle Nichols in New York; Editing by Giles Elgood, Rosalba O'Brien and Himani Sarkar