HONG KONG — Hong Kong police said Monday that a homemade remote-controlled explosive device intended to “kill or to harm” police officers was detonated during protests Sunday, in a further escalation of violence from anti-government unrest now in its fifth month.

"It exploded less than 2 meters (yards) away from a police vehicle. We have reason to believe that the bomb was meant to target police officers," Deputy Commissioner Tang Ping-keung said at a news conference, speaking through a translator.

No casualties were reported. Tang said it was the first known use of an explosive device during the protests that started in June over a contested extradition bill and have snowballed into an anti-government, anti-police and anti-China movement.

Chin-chiu Suryanto, an officer with the police force's bomb-disposal unit, said the device was concocted with a "highly effective" explosive.

He said there was "a loud thud" from the detonation Sunday night on a usually busy thoroughfare in Kowloon.

He said the use of an explosive device marked an escalation in violence seen during the anti-government protests. He likened the use of such a device to “terrorist events” seen elsewhere in the world.