At least 20 people were killed during the Haiti Carnival in the early hours of this morning when they were electrocuted by a power line falling on their packed float.

The accident happened as thousands of people filled the streets of central Port-au-Prince, the Caribbean country's capital, for the raucous annual celebration.

Witnesses at the scene said someone on the float used a pole or stick to move a power line so the float could pass under it, but video appeared to show it striking the head of a singer riding on top.

Meanwhile in the southeastern Brazilian city of Nova Iguacu, three men were killed in eerily similar circumstances when their carnival float ran into a power line.

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Electric shock: The moment a performer on top of a float at the Haiti Carnival got caught by an overhead power line as the parade passed through the streets of Port-au-Prince in the early hours of the morning

Chaos: The scene seconds after the performer was electrocuted. Witnesses said the float then caught fire and performers leapt off causing a stampede among the thousands of revellers packed into the streets

Carnival disaster: Thousands of Haitians throng the streets of Port-au-Prince, hampering the movement of ambulances minutes after a power line fell onto a Carnival parade float and killed at least 18 people

Confusion: Hundreds of people crowd around the float just after the power line strike

Emergency response: Ambulances and paramedics at the scene of the accident in the early hours of the morning. Witnesses said the power line fell after someone tried to use a pole or stick to move it

First responders: Paramedics carry away an injured person after the accident at around 2.48am

Seven people were reported dead on the float, which caught fire after the flash of sparks, Reuters reported. Others managed to jump off, leading to more deaths and injuries in the densely packed crowd of spectators as people began to panic.

A further 46 people were injured in the accident, according to Nadia Lochard, a coordinator for the Department of Civil Protection. Reuters put the toll of injuries at 60, without citing a source.

The float was sponsored by the Haitian hip-hop group Barikad Crew. An unverified video posted to YouTube and on social media today shows a rapper from the group hit in the head by an exposed power line while riding a tall float.

A second YouTube video shows crowds parting as paramedics race to the scene in an ambulance.

'I saw the wire falling and sparks and I started running for my life,' said Natacha Saint Fleur, a 22-year-old who was near the float at the time.

Dr Joel Desire at the General Hospital, where many of the victims were taken, said at least 18 people died. It was not immediately clear if other victims had been taken elsewhere.

Hundreds of people thronged the hospital, some carrying victims and others searching for family members taken there by ambulance.

Mutual aid: Revellers, still dressed in their carnival garb, wait outside the General Hospital in Port-au-Prince

Hospitalised: A security guard directs proceedings as an ambulance carrying injured people arrives

Making do: A woman is wheeled inside the poorly equipped hospital on a makeshift wheelchair

Assessing the situation: Doctors perform a triage examination on a man after he's brought to hospital

Injuries: Victims receive treatment at the emergency room of the General Hospital

Treatment: A doctor squeezes a bag connected to an intravenous line into a patient hurt in the disaster

Crisis: Doctors prepare to treat an injured woman carried by a friend into the emergency room

Overcrowding: A man lies on the floor as he waits for treatment at the hospital, which was packed with people

Grief: A woman cries after learning of the death of a family member in the accident this morning

Waiting: Police hold back a crowd of people outside the General Hospital waiting for news of the injured

Concern: Worried expressions spread across the faces of waiting friends and relatives outside the hospital

Desperate: People peep through a hole in the wall of the General Hospital mortuary in an effort to catch a glimpse of the dead bodies to see if their loved ones are among them

Tragedy: A woman walks away from bodies after failing to find a missing relative among them

President Michel Martelly expressed his 'sincerest sympathies' to the victims in a Twitter message.

A statement by Haiti's Minister for Information, Rotchild Francois jr, carried on the Dynasty Haiti website, said: 'The Government of the Republic informs the public that an unfortunate accident, following an electric shock, happened earlier this morning at 2.48am when Barikad Crew's carnival float passed through the area of the Champ de Mars in the course of the second day of the National carnival 2015.

'A preliminary assessment allows for more than a dozen dead and forty wounded. The government offers its sympathies to the families of the victims and said that all arrangements have been made to assist all those affected by this tragedy. The public will be kept informed of developments.'

Strikes twice? A man looks up at power lines as he stands along with others on the street where the carnival float hit the power lines hours earlier, when the carnival party was in full swing

Nervous: People gathered at the spot where the accident happened, staring warily up at the power lines

The disaster will be a blow for Haiti's battered economy, which is still recovering from a massive earthquake in 2010 that killed as many as 200,000 people.

Known in the local Creole language as 'Haitian Defile Kanaval', Haiti's Carnival is said to be one of the largest Mardi Gras carnivals in the Caribbean and North America.

The celebrations, which are funded by the government, businesses and wealthy Haitian families, were to climax today, Shrove Tuesday, known in French as 'Mardi Gras' - meaning 'Fat Tuesday'.

Party time: Dancers file past in a Carnival parade to the national palace in Port-au-Prince yesterday

Letting loose: Haiti's Carnival is said to be the biggest Mardi Gras carnival in the Caribbean

Costumes: The disaster will cast a dark cloud over the Carnival finale today

In Brazil, the Palmerinha samba school was getting ready to go on parade when one of its floats hit a power line, electrocuting the three men riding it.

Emergency personnel tried to revive them, but without success, according to the Globo G1 news site.

In Rio, police used tear gas to disperse crowds when a street party degenerated into a brawl in the Complexo de Alemao, one of the city's toughest favelas, images on Globo TV showed.

Police in Sao Paulo also resorted to tear gas early Tuesday after revellers in the hip Vila Madalena neighborhood refused to heed a 1:00 am closing time set by the authorities.