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.

Xi urged "decisive actions" against "terrorists" in the aftermath of the attack.

"The battle to combat violence and terrorism will not allow even a moment of slackness, and decisive actions must be taken to resolutely suppress the terrorists' rampant momentum," state news agency Xinhua quoted Xi as saying.

CCTV said assailants attacked crowds with knives and set off explosions at the same time at the Urumqi South Station.

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, Xinhua reported.

A woman working at a convenience store near the train station said she heard a loud explosion shortly after 7 p.m. local time.

"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 tension runs high in Xinjiang

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, according to official figures.

Despite a heavy crackdown, violence has continued in the region and began spreading elsewhere in the country last year.

Rian Thum, a professor at Loyola University in New Orleans, who specializes in Uighur history and issues, said the use of explosives and the location of Wednesday's blast were significant.

"Violence in Xinjiang has previously tended to target security personnel and officials, often carried out with knives or farm tools. A bomb attack targeting civilians, if that is what this is, would mark an alarming deviation from previous patterns of Uighur political violence," Thum said.

"Of course, we can't yet assume that the attack was intentional, or that it was carried out by Uighurs, though it seems likely that it was both," he said.

Uighurs behind other recent attacks

Last year, three Uighurs rammed a vehicle into crowds in a suicide attack near the Forbidden City gate in the heart of Beijing, killing themselves and two tourists.

In March, five knife-wielding men and women believed to be Uighurs slashed at crowds indiscriminately at a railway station in southwestern China, killing 29 people. The government has blamed the attack on secession-seeking terrorists.

While Beijing faults separatists for raising ethnic tensions, government critics say restrictive and discriminatory policies and practices have alienated the Uighurs. They say Han people have flooded Xinjiang and benefited from its economic growth while Uighurs have felt excluded.