BEIJING (REUTERS, AFP) - Chinese police shot dead dozens of knife-wielding attackers on Monday morning after they staged assaults on two towns in the westerly Xinjiang region, the official Xinhua news agency said on Tuesday, citing local police.

It said a gang armed with knives had first attacked a police station and government offices in the town of Elixku, in Shache county, and some then moved on to the nearby town of Huangdi, attacking civilians and smashing and setting fire to vehicles.

Xinjiang, home to many Turkic-speaking Uighurs, has for years been beset by violence, which the government blames on Islamist militants or separatists who it says are bent on establishing an independent state called East Turkestan.

It was not clear why the attack was only being reported on Tuesday, more than a day after it took place.

"A gang armed with knives and axes attacked a police station and government offices" in the county, the official Xinhua news agency said, citing local police. "Dozens of Uighur and Han civilians were killed or injured" when some moved to a nearby township, attacking civilians and smashing vehicles, the report said.

"Police officers at the scene shot dead dozens of members of the mob," it added.

The attack came on the eve of Muslims in China marking the Eid festival at the end of the fasting month of Ramadan. Dilxat Raxit, a spokesman for the exile World Uyghur Congress, an exile group, said in an e-mail that more than 20 Uighurs were shot dead by armed authorities while 10 were injured. A total of 13 Chinese security personnel were killed and injured, he said citing what he described as a local source, and about 67 people were arrested.

Information in Xinjiang is often difficult to verify independently and it is not unusual for there to be a time lag in official media reporting violent incidents, especially when they involve clashes with police. In a bylined commentary Xinhua said that the attack was intended to "destabilise the region and spread fear and hatred".

"Police shooting dead of the mobsters was decisive and well justified," it said. "The attack is against the spirit of Ramadan, which is about the practice of self-discipline and self-control," it added. "The rioters were committing blasphemy against Islam, 'the religion of peace'."

Beijing commonly blames separatists from Xinjiang for carrying out terror attacks which have grown in scale over the last year and spread outside the restive region. Among the most shocking incidents was a market attack in Xinjiang's capital Urumqi in which 39 people were killed in May, and a deadly rampage by knife-wielding assailants at a train station at Kunming in China's southwest in March, which left 29 dead.

The violence has also included a fiery vehicle crash at Tiananmen Square, Beijing's symbolic heart, in October. Rights groups accuse China's government of cultural and religious repression they say fuels unrest in Xinjiang, which borders Central Asia.

The government, however, argues it has boosted economic development in the area and that it upholds minority rights in a country with 56 recognised ethnic groups. The latest reported violence comes as China has launched a crackdown following the high-profile attacks, making a show of punishing offenders.

Earlier this month courts in Xinjiang sentenced 32 people to prison terms ranging from four years to life for terrorism-related charges, state media reported. In June, authorities executed 13 people, and sent more than 100 to jail in a public mass sentencing on mostly terrorism-related offences in Xinjiang. Three people were also sentenced to death for the Tiananmen Square attack.

In early July, government websites said China banned civil servants, students and teachers in Xinjiang region from taking part in Ramadan fasting, leading to condemnation from the World Uyghur Congress. China's ruling Communist party is officially atheist, and for years has restricted fasting in the region.