BEIJING - An explosion rocked a railway station in China's restive far-western region of Xinjiang, and the state broadcaster said three people were killed and 79 people were injured. The attack Wednesday came as President Xi Jinping wrapped up a four-day visit to the area.

CCTV said assailants attacked crowds with knives and set off explosions at the same time at the Urumqi South Station. The station called it a terrorist act.

It was unclear whether Xi was still in the region at the time of the blast, which occurred at the rail station in the regional capital of Urumqi.

Train service was suspended for about two hours before it reopened under the watch of armed police, the official Xinhua News Agency said.

A woman working at a convenience store near the train station said she heard a loud explosion shortly after 7 p.m. "The whole area now has been cordoned off by police and military police," said the woman, who spoke by telephone and refused to give her name because of the sensitivity of the matter.

Photos circulating briefly on Chinese social media sites showed scattered luggage near the station's exit and a heavy presence of armed men. Xinhua said the blast was centered on some luggage left on the ground between the station's exit and a bus stop.

Ethnic tensions have been simmering for years in Xinjiang, the home of the Muslim Uighur minority group. In 2009, a series of riots broke out in Urumqi, leaving nearly 200 people dead.