(CNN) -- Pre-dawn clashes in a remote northwestern county Sunday killed at least eight people, including a security guard, after assailants using handmade explosives attacked police and government facilities, China's state-run Xinhua reported.

A bombing broke windows and scattered debris Sunday at Hualin Market in northwest China's Kuqa County.

Chinese authorities cordoned off the area and ordered all businesses closed in Kuqa County, located in the Xinjiang Uighur Autonomous Region, which borders Tibet. The county is home to about 400,000 people.

Xinhua reported that seven attackers were among those killed, four of them by suicide. Last month, officials said they cracked five terrorist groups in the autonomous region that allegedly were plotting to sabotage the Summer Olympics in Beijing, about 1,740 miles (2,800 km) from Kuqa County.

Sunday's attacks began about 2:30 a.m. with an explosion at a public security bureau. The blast killed a security guard and wounded two police officers and two civilians, Xinhua said. Watch how the region has become volatile »

Police fatally shot one of the attackers and captured another one. A third bomber killed himself, the news agency reported.

Hours later, police located five attackers hiding under a market counter and shot two of them dead. The other three committed suicide, Xinhua said.

Authorities said 15 people -- using explosives made of pipes, gas canisters and liquid gas tanks -- took part in 12 bombings.

An attack in the same region Monday killed 16 police officers and injured 16 more when two men crashed a dump truck into a group of police officers before throwing at least five homemade bombs into their barracks.

The Xinjiang Uighur Autonomous Region -- also called East Turkistan -- is home to a Sunni Muslim ethnic minority. Uighurs in Xinjiang are supposed to enjoy regional autonomy, as guaranteed by China's constitution, but some seek independence.

Millions of Han Chinese, the country's dominant ethnic group, have migrated into Xinjiang over the past 60 years, prompting complaints that they dominate local politics, culture and commerce at the Uighurs' expense.

The dissatisfaction has turned violent at times, including several sometimes-deadly bus bombings in 1992 in the provincial capital, Urumqi. Officials blamed such incidents on Uighur groups seeking an independent Muslim state.

China insists that only a small minority of Uighurs support the separatists.

The regional public security department said it received intelligence suggesting that the "East Turkistan Islamic Movement" planned to make terrorist attacks between August 1-8, Xinhua reported.

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