BEIJING — China’s state news media on Tuesday belatedly reported what was described as a terror attack in the troubled far west region of Xinjiang, where dozens of people were said to have been killed or wounded by assailants with knives and axes.

The incident occurred on Monday, the official news agency Xinhua and other state outlets reported. It was not clear why the authorities had taken more than a day to release the news, although much of the violence in the region goes unreported by China’s tightly controlled news media.

Exile groups immediately disputed the government’s account, saying the bloodshed had occurred when security forces opened fire on a group of people protesting government restrictions on the celebration of Ramadan, the Muslim holy month, and an earlier extrajudicial killing by the police.

The confrontation took place in the fertile crescent of southern Xinjiang, the scene of mounting violence. According to Xinhua, it began at a government building in Yarkant County and spread to surrounding streets, where assailants attacked passers-by and set cars on fire.