The famous giant portrait of Chairman Mao which hangs in Tiananmen Square in Beijing has been damaged by fire, with some reports saying it was vandalised.
Witnesses say they saw flames and smoke coming from the painting
Witnesses say they saw flames and smoke coming from the painting and pictures showed scorch marks at its bottom.
One unconfirmed report said the damage was caused by someone who threw a burning object.
Large numbers of police cleared the area after the incident and workers have been seen cleaning the portrait.
Xinhua news agency said police detained Gu Haiou, a 35-year-old unemployed man from Urumqi, in the far north-western region of Xinjiang, though the report did not specify the grounds for his detention.
An official at the Tiananmen Administration Committee confirmed there had been an incident but said he had no details.
The picture was defaced during the Tiananmen Square pro-democracy demonstrations in 1989.
The protestor responsible, a Chinese journalist, spent 16 years in jail for hurling eggshells filled with red paint at the portrait.
The area around Tiananmen Square is usually patrolled by plainclothes security who quickly stamp out any signs of dissent.
Mao Zedong founded the People's Republic of China in 1949 and is still revered by many in the country who see him as a symbol of its strength and unity.