Assailants set off explosives and slashed indiscriminately at passengers at a railway station on Wednesday, officials and state media said.

One large blast took place shortly after 7pm local time at the exit of the Urumqi South Railway Station, and appeared to originate from luggage left on the ground between the station and a public bus stop, according to Chinese media reports.

"The attackers used knives to stab people at the station exit, and detonated explosives at the same time," Xinjiang's local government portal said, adding the injured had been taken to hospital. "The explosion at Urumqi South Railway Station was a serious and violent terrorist attack."

President Xi urged "decisive actions against violent terrorist attacks" following the incident.

It was not immediately clear who the attackers were or how many orchestrated the attack, but it was reminiscent of a similar incident in March which stunned China.  A group of knife-wielding Uighurs slashed at commuters, killing 29, at a train station in Kunming, which was also condemned as a premeditated terrorist attack by the Chinese government.

On Wednesday, photographs that circulated on social media showed blood on strewn luggage and charred debris in front of the railway station exit in Urumqi.

The station reopened two hours after the explosion, according to state media.

Xinjiang has been plagued with deadly violence involving members of the Uighur ethnic minority. More than 100 deaths have been reported from the region in the past year, often because of conflict between Uighurs and local police.

In his visit to Xinjiang, which has dominated state media coverage in recent days, Mr Xi has endorsed policies designed to better integrate the Muslim Uighur ethnic minority while warning that China would not tolerate separatist violence.

On a visit to a mosque in Urumqi on Wednesday, Mr Xi said he hoped religious people would continue their patriotic tradition and take a clear stance against extremism.

"The long-term stability of Xinjiang is vital to the whole country's reform, development and stability; to the country's unity, ethnic harmony and national security as well as to the great revival of the Chinese nation," Mr Xi said, according to official news agency Xinhua.

Touring a police station in Kashgar on Monday, he said the border region was the "frontline in anti-terrorism efforts and maintaining social stability" and urged police officers he met to devise "effective ways" to deal with the threat.

"The training must simulate real combat," he said. "Sweat more in peacetime to bleed less in wartime."

State television reports also showed Mr Xi chatting with locals around a table adorned with traditional Uighur snacks, and wearing the traditional green "doppa" headwear favoured by many Uighur men.

Mr Xi has also made regular comments around strengthening national security in what analysts have considered signalling a tougher approach to dealing with the recent violence in Xinjiang.

"[We must] make terrorists become like rats scurrying across a street, with everybody shouting 'beat them!'" Mr Xi said at a national security study session on Friday.

The Chinese government considers the spate of violence in Xinjiang to be motivated by Muslim separatists calling for independent rule. However Uighur rights groups say the violence has stemmed from a desperate reaction to worsening discrimination and restrictions on their freedom of religion.