Eight people have been killed and at least 11 injured in an "act of terror" after a man drove a pick-up truck onto a path for cyclists in New York City.
The 29-year-old driver was shot by police in the abdomen and taken into custody after he crashed the truck into a school bus and fled his vehicle, according to New York City Police Commissioner James O'Neill.
He also said that police would not identify the driver at this time.
Speaking at a press conference, New York Mayor Bill de Blasio said the attack was "a particularly cowardly act of terror".
Mr de Blasio said: "It's a very painful day in our city. Horrible tragedy on the West Side.
"Let me be clear, based on the information we have at this moment, this was an act of terror and a particularly cowardly act of terror. Aimed at innocent civilians, aimed at people going about their lives who had no idea what was about to hit them.
"We at this moment based on the information we have, we know of eight innocent people who have lost their lives. And over a dozen more injured."
New York Governor Andrew Cuomo said the suspect appeared to have acted alone.
He said: "There's no evidence to suggest a wider plot or a wider scheme. These are the actions of one individual meant to cause pain and harm and probably death."
Mr O'Neill said the driver was armed with a paintball gun and a pellet gun.
The driver hit a school bus, injuring two children and two adults on board before exiting the pick-up truck.
The man was shot in the abdomen by a uniformed officer before being taken into custody.
The commissioner said a statement made by the suspect when he exited the vehicle was "consistent" with a terrorist attack.
In a statement, US President Donald Trump said his administration will provide "full support to the New York City Police Department, including through a joint investigation with the Federal Bureau of Investigation."
He said that he will continue to follow developments closely.
Hours after the attack, Mr Trump tweeted: "We must not allow ISIS [IS] to return, or enter, our country after defeating them in the Middle East and elsewhere. Enough!"
Authorities have not definitively linked the suspect who was detained to the so-called Islamic State group.
Earlier, Mr Trump said the attacker was "very sick" and a "deranged person".
In NYC, looks like another attack by a very sick and deranged person. Law enforcement is following this closely. NOT IN THE U.S.A.!— Donald J. Trump (@realDonaldTrump) October 31, 2017
Jim Dwyer, New York Times journalist says the Manhattan foot path where the attack took place is usually 'a very heavily trafficked pathway' pic.twitter.com/VYtRif5pUD— RTÉ News (@rtenews) October 31, 2017
British Prime Minister Theresa May tweeted: "Appalled by this cowardly attack, my thoughts are with all affected. Together we will defeat the evil of terrorism. UK stands with #NYC."
PM: Appalled by this cowardly attack, my thoughts are with all affected. Together we will defeat the evil of terrorism. UK stands with #NYC— UK Prime Minister (@Number10gov) October 31, 2017
A police spokesman posted a photo showing a white pick-up truck on the bike path with its front end mangled and the hood crumpled.
The rented truck had logos of the Home Depot hardware store chain.
Mangled and flattened bicycles littered the bike path, which runs parallel to the West Side Highway on the western edge of Manhattan along the Hudson River.
One witness told reporters at the scene that he heard about five gunshots before seeing a large man being taken into custody.
"He seemed very calm," the witness said. "He was not putting up a fight."
Emergency services at the scene after pickup truck drives onto footpath and cycle lane in Lower Manhattan – several people have been killed pic.twitter.com/7tvDeCzxoa— RTÉ News (@rtenews) October 31, 2017
A witness told ABC Channel 7 that he saw a white pick-up truck drive south on the bike path at full speed and hit several people.
A video apparently filmed at the scene and circulated online showed scattered bikes on the bike path and at least two people lying on the ground.