Dozens of civilians were killed or injured in a terrorist attack early Monday morning in Shache county, Kashi Prefecture, Northwest China's Xinjiang Uyghur Autonomous Region, local police were quoted by the Xinhua News Agency as saying.

A gang armed with knives attacked a police station and government offices in Elixku township, and some moved on to the nearby Huangdi township, attacking civilians and smashing vehicles as they passed. Dozens of Uyghur and Han civilians were killed or injured, according to police.

Police officers at the scene shot dead dozens of members of the mob.

Authorities did not reveal the exact number of terrorists or casualties.

A source told the Global Times that the violence occurred after officers detected suspicious explosives, the source said.

Xinhua said that 31 cars were vandalized, with six set on fire.

Initial investigations showed that it was a premeditated terror attack, police said, adding that further investigation is underway.

The attack took place during the 10th Kashi Central & South Asia Commodity Fair, which kicked off on Sunday and was scheduled to last for three days.

The fair has ended earlier than scheduled and many businessmen are quite angry, one Uyghur businessman told the Global Times. "Every time we see hope [of development] there are people creating violent incidents," he said.

It is unknown whether the terrorists had specifically picked this date to sabotage the commodity fair, the largest trade event in southern Xinjiang which aims to bring investment and technology as well as boost the local economy.

The attack happened a day ahead of the traditional holiday that marks the end of the Islamic holy month of Ramadan.

Security has been ramped up over the whole region.

The attack is one of multiple terror incidents in Xinjiang in recent months. 

On May 22, explosions in an open-air market in Urumqi, capital of Xinjiang, left 39 dead and more than 90 injured.

On April 30, three people were killed and another 79 injured in a terror attack involving self-made explosives at a railway station in Urumqi.

A year-long anti-terror campaign was launched after the May 22 bombing. In late June, 32 gangs were busted, over 380 suspects apprehended and 315 people convicted in the first month of Xinjiang's anti-terror campaign. To guard against possible terrorist attacks, police authorities nationwide have beefed up armed patrols and taken other precautions.