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.