A small homemade bomb has exploded outside the US embassy in Beijing and wounded the lone assailant, the embassy says, but police described the weapon merely as a "firework device".
The blast happened on Thursday in a public space off the southeast corner of the embassy compound.
Beijing police say the suspect, a 26-year-old man from China's Inner Mongolia region, was injured on the hand by the explosive device, which was made from fireworks and detonated about 1pm (3pm AEST).
No damage was done to embassy property and no other injuries were recorded, according to a US embassy spokesperson.
Photos on social media showed a large amount of smoke and police vehicles surrounding the embassy shortly after the incident.
Apart from a heightened security presence, the scene outside appeared to be normal by early afternoon.
Police did not provide a motive but China and the US have been involved in an escalating trade dispute initiated by the Trump administration after the two sides imposed tariffs on $US34 billion ($A46 billion) worth of each other's goods.
Witnesses told Reuters they heard an explosion near the embassy and felt tremors.
A police SUV appeared to have been damaged, with its back windshield missing, and was cordoned off by police before being removed, a Reuters witness said.
Crowds were still queueing outside the embassy after the explosion and traffic was moving as usual in an area of northeastern Beijing that is home to numerous embassies including those of France, India and Israel.
Staff members at the Indian and South Korean embassies said they were unaware of any unusual incident and were working as normal.
In the initial confusion, there were conflicting reports about what had happened.
An earlier report in the Global Times, a newspaper run by the ruling Communist Party's People's Daily, said police had removed a woman who had sprayed herself with gasoline in a suspected self-immolation attempt.
America remains a hugely popular destination for travel, education and immigration for Chinese citizens.
On weekdays, large lines of visa applicants form outside the embassy, which sits in a busy corner of the city hosting numerous diplomatic installations as well as hotels and stores.
