San Francisco police are working with the FBI to investigate a "despicable" arson attack on the Chinese consulate on New Year's Day.
The attack happened in the evening when a man jumped out of a minivan that was parked outside the consulate and poured two buckets of petrol on the front doors and lit it.
Watch: Arson attack at the Chinese consulate in San Francisco
A consulate spokesman said the fire caused a lot of damage but there were no injuries.
"The arson attack is a violent crime targeted at the Chinese consular institution in the United States, causing severe damage to the consulate facilities and posing a threat to the safety of the consulate staff and the residents living nearby," the spokesman said in a notice posted on the consulate website.
"We strongly condemn this despicable act and have already made representations with the US side on the attack.
"We urge the US side to take all necessary measures to provide adequate protection for Chinese consular personnel and properties and bring the culprit to justice as soon as possible."
The fire was reported about 9.30pm and was brought under control soon afterwards.
Online users posted pictures on Twitter and weibo showing a man pouring the petrol on the consulate's main entrance.
"I could feel the heat even though I was sitting inside my car. Everyone was trying to call the police," one online user said. "I could also hear ambulances coming towards the consulate general."
It is not the first time the consulate has been attacked.
Flammable liquid was poured on a metal door at the consulate in 2008 amid controversy over China's crackdown against protesters in Tibet.
The crackdown triggered major demonstrations at Chinese embassy buildings around the world.