The pre-dawn violence in the restive Muslim region of Xinjiang came despite tightened security for the games and followed threats by an al-Qaeda-linked militant Islamic group that it would disrupt the sporting event.

Police said in a brief statement that “violent terrorists” attacked a shopping center, hotel and government buildings in the city of Kuqa in west central Xinjiang. Without providing details, it said officers killed eight attackers and two others blew themselves up, while two were arrested. Three attackers were at large, it said.

In a more detailed account, the state-run Xinhua News agency said the bombs were made from bent pipes, gas canisters and liquid gas tanks. In one of the largest attacks, assailants drove a three-wheeled vehicle with explosives into the compound of the public security bureau at about 2:30 am, Xinhua reported. An explosion followed that killed the security guard, injured two police and two civilians, and destroyed two police cars, it said.

Police opened fire on the attackers, killing one. Another blew himself up, injuring a third, and a fourth was captured in the assault, Xinhua said, citing an unidentified local government spokesman.

Six hours later, a battle broke out in a nearby market where police found five attackers hiding under a counter, Xinhua said. The men hurled bombs at the police, who fatally shot two of them, while the remaining three killed themselves with their own bombs, the news agency said.

Xinhua said the captured suspect told police that 15 people were involved in the attack.

Police declined to confirm the Xinhua account or comment on the discrepancies between it and the police statement.

The already-tight security in Xinjiang was increased after assailants killed 16 border police and wounded 16 others in Kashgar city on August 4, ramming a stolen truck into the group before tossing homemade bombs and stabbing them.

The attacks mark a dramatic increase in violence in Xinjiang, where local Muslims have waged a sputtering rebellion against Chinese rule. Heavy security had largely succeeded in suppressing violence over the past decade.

Wang Wei, vice president of the Beijing Olympic Organizing Committee, called the attacks the work of “East Turkestan terrorists” — the name some separatists use for Xinjiang — and said no government would tolerate such violence.

“The very purpose of these attacks is all about separating the region from China,” Wang told reporters. He said the attackers “want to use the Olympic stage to enlarge the impact.”

Authorities shut down Kuqa county, a region 2,800 km west of Beijing where some 4,00,000 people live, for most of the day. Soldiers with machine guns patrolled the streets and people were told not to leave their homes. A Foreign Ministry official in Beijing, speaking on customary condition of anonymity, said the restrictions were akin to martial law.