Haiti's interim Prime Minister Garry Conille has vowed to end lawlessness with the help of a Kenyan-led international force deployed to the Caribbean nation.

The arrival of 400 Kenyan police officers, in the first tranche of an international force, was a "unique opportunity" to restore order, Mr Conille said.

“I want no-one to doubt the purpose of the mission. The state will regain power and reaffirm its authority so all Haitians can live peacefully in this country," he said.

Rocked by decades of instability, the Caribbean nation has seen an escalation of violence following the assassination of President Jovenel Moïse three years ago.

US President Joe Biden also welcomed the deployment, saying the Kenyan-led mission offered the "best chance" to achieve democratic governance in Haiti.

But there is fierce opposition in Kenya to the deployment - not least because police are accused of brutality in their own country, the latest example being the fatal shooting of protesters in the capital, Nairobi, on Tuesday.

The unrest in Nairobi came a day after President William Ruto saw off the officers, in what he described as a "historic" mission of solidarity.

Rival armed groups took control of the capital, Port-au-Prince, earlier this year, forcing Prime Minister Ariel Henry to resign weeks later.

Armed gangs now control an estimated 80% of the city.

A "robust use of force" is needed to tackle them, says the UN, which has approved a policing mission made up of 2,500 officers from various countries - including 1,000 pledged by President Ruto, though only 400 have so far been deployed.

Working with Haitian police, and headquartered at a US-built base, the Kenyan officers will aim to take back key sites that have fallen under the control of gangs, including the nearby airport and sea ports.

Haiti has not had an election since 2016. So elections are to be organised within a year, and to allow that to happen, the Kenyan-led mission is being tasked with restoring security.

Their deployment has been authorised for one year, with a review to be held after nine months.

Gang violence on average killed or injured more than one person per hour in the first three months of this year, according to UN data.

Close to 600,000 Haitians have been forced from their homes, according to the UN's migration agency.

Schools and police stations have in some places been turned into shelters by families fleeing the violence.

Haiti's police force has just 9,000 officers. By contrast, it is estimated that as many as 8,000 Haitians belong to 200 or so armed gangs - with roles ranging from commanders to informants. Recruitment has increased in recent years.

The gangs now have as much firepower as the police, says Emmanuel Paul, a security adviser who works with humanitarian groups in Haiti.

"Virtually the same types of weapons are used on both sides - classic assault rifles, AK-47 Kalashnikovs of various makes," he tells the BBC.

Colombia's President Gustavo Petro has even accused the military in his country of selling missiles and ammunition to armed men, who could have smuggled them into Haiti.

"We are doing it for the people of Haiti. The responsibility for security in Haiti is a shared responsibility," says Mr Ruto.

But critics say Kenya is merely doing the bidding of the US and hopes to curry favour with the superpower, especially on the security front.

On a recent visit to Washington, Mr Ruto also mentioned wanting to boost Kenya's international standing in this arena.

The East African nation's subsequent designation as a major non-Nato ally by the US has certainly achieved that.

But at home, President Ruto is facing significant opposition and Kenya’s High Court has ruled that the deployment is unlawful. This delayed the arrival of the first officers.

The court stated that the Kenyan government had no authority to send police officers abroad without a prior reciprocal agreement.

Such an agreement was signed on 1 March, but opposition party Thirdway Alliance Kenya has filed a fresh lawsuit, arguing that the deployment remains in breach of the law.

"This mission is sanctioned by the United Nations (UN). The request came from the UN and the US. There is no request by Haiti, neither is there one that is capable of being put in place," says Charles Midega, a lawyer for the petitioners.

"The president has not followed the procedure as per the Kenyan constitution and laws on deployment. And most importantly, the president has not gazetted Haiti as a reciprocating country as a pre-requisite for deployment."

Although Kenya has a history of taking part in peacekeeping missions, its police force has never set foot outside Africa.

It is believed that the deployed unit will come from the General Service Unit (GSU), a paramilitary wing often deployed during demonstrations and terrorist attacks.

It has not previously been used against international criminal networks like the Haitian gangs.

But the Kenyan government said the deployed officers had received specialised training, including lessons in French and Haitian creole to ease communication with their counterparts.

Another hurdle in sight will be the chain of command.

"There are going to be Kenyan police, but other countries are sending soldiers," says Mr Paul.

"That's going to be the first headache of the mission - how to coordinate the police and the military, given that they have different training backgrounds and have different missions."

Newly appointed commander Godfrey Otunge will be spearheading the Kenyan taskforce and will have a big task on his hands.

Kenya's police officers have long been criticised for human rights abuses, and several rights groups have expressed concerns about their deployment to Haiti.

On Tuesday, police in Kenya' capital, Nairobi, were accused of using live rounds against anti-tax hike protesters.

The Kenya Medical Association said that at least 13 people were killed.

Mr Ruto defended the police, saying "legitimate" protests had been "hijacked by a group of organised criminals."

In a letter to the UN Security Council last August, Amnesty International highlighted the Kenyan police's record of using excessive force.

It also accused Kenyan police of killing dozens of protesters last year and unlawfully arresting and detaining others.

But police chief Japhet Koome denied this, and last year accused opposition politicians of planting bodies hired from mortuaries at protest scenes in order to pin the deaths on his personnel.

Haiti has seen three major peacekeeping mission in the last 30 years, which have all failed to prevent the crisis getting worse.

In 1994, some 25,000 military personnel from Caribbean nations were sent under a UN-mandated operation.

Ten years on, 9,000 UN peacekeepers led by Brazil and known as Minustah were sent.

This time around, it is believed that the UN-mandated taskforce will total 3,000 officers at most, including civilians contractors deployed on site for logistical support.

Haiti's transitional presidential council recently appointed Mr Conille, a former prime minister, to lead the country until elections are held.

Haitians have seen peacekeeping missions come and go, with no stability achieved.

They will be hoping for a different outcome this time around.

Additional reporting by Natasha Booty