At least five people have been killed in Kenya's capital, Nairobi, as police clashed with supporters of opposition leader Raila Odinga.

Officers on Friday used tear gas and water cannon to break up large crowds cheering Odinga's convoy from the airport to central Nairobi, after his return to Kenya from a trip abroad.

Odinga, leader of the National Super Alliance (NASA), said in a statement that authorities had also used "armed militia and live bullets" to disperse supporters, which led to the "killing [of] several and maiming [of] many".

My statement on the use of unprecedented and unnecessary force by the Jubilee regime on NASA supporters who formed my welcoming party, today #Resist pic.twitter.com/hP1NRr9vj2 — Raila Odinga (@RailaOdinga) November 17, 2017

Amnesty International urged Kenyan police to stop using live ammunition, saying it had received reports of at least three deaths, while TV footage showed another man being shot in the leg.

"Firearms can only be used when strictly unavoidable in order to protect life," said Abdullahi Halakhe, the group's East Africa researcher.

"The indiscriminate use of live ammunition is totally unacceptable. Firearms must never be used to disperse crowds."

Police admitted using tear gas and water cannon but denied the usage of live ammunition.

In a statement, the National Police Service said five people were stoned to death by angry crowds after being caught looting.

"Sections of the mobs accompanying the NASA convoy looted property, and five persons were killed by stoning in different incidences after having been caught stealing by enraged crowds. Two were stoned along Landies Road, two next to country bus station and one along Racecourse Road," the statement said.

Police said the incidents took place before officers arrived at the various scenes, adding that the deaths were being investigated.

Al Jazeera's Fahmida Miller, reporting from Nairobi, said "thousands of opposition supporters had gathered to listen to an address from Odinga on his return to the country after a visit abroad, ending in these running battles with the police.

"The supporters had tried to make their way to the city centre anticipating that address from Odinga. The opposition leader was able to briefly address his supporters on the road after they were blocked from moving to the centre of Nairobi," she added.

"Earlier in the day, opposition supporters had lit tyres on main roads and thrown stones at police."

Court decision

Odinga has vowed to embark on a political campaign to "restore democracy in the country", and called for a "resistance movement" to protest against the outcome of a presidential election rerun last month, which saw President Uhuru Kenyatta win a second term with 98 percent of the vote.

The repeat poll, which was boycotted by Odinga, was ordered by Kenya's Supreme Court after it annulled the results of an August election over irregularities.

The court will make a decision on Monday on cases that seek to nullify the rerun vote.

"So far, various rights groups say between 60 and 70 people have been killed in protests, that began before the August presidential election and continued through to the rerun held last month," said Miller.

"These protests took place mostly in areas in the capital or the west of the country where the opposition has a lot of support."