The explosion on Wednesday, which state news agency Xinhua called a "violent terrorist attack", came on the same day that President Xi Jinping ended a visit to the restive region.

The blast occurred at around 7pm local time at the south railway station in Urumqi, Xinhua news agency said.

It added that the explosion was "centered around luggage left on the ground between the station exit and a public bus stop," citing witnesses.

Ambulances and police cars rushed to the scene, Xinhua said.

The station was closed after the incident and services suspended but it has since been reopened. Police evacuated people from nearby areas, the state news agency quoted an officer as saying.

Initially witnesses posted photos on social media site Weibo, showing debris and luggage scattered around, though these were not independently verified.

Many posts relating to the explosion have since been removed, including images from apparent witnesses, and posts from news organizations detailing the incident.

The vast and nominally autonomous region of Xinjiang, where mostly Muslim Uighurs are the largest ethnic group, is periodically hit by deadly clashes that authorities blame on terrorists.

Xi, during a visit which ended Wednesday, called for tougher law enforcement but also for stepped-up assimilation of minorities.

While fighting terrorism, China will deploy a "strike-first" strategy against terrorists in the region to deter enemies and inspire people, Xinhua quoted him as saying.

But he added that Beijing would implement "appropriate policies to improve ethnic harmony and common prosperity of all ethnic groups".

HH/HH