Image copyright AP Image caption Security was tight outside the station following the explosion

A bomb and knife attack at a railway station in China's western Xinjiang region has killed three and injured 79 others, officials and state media say.

The attackers used explosives and knives at Urumqi's south railway station on Wednesday, officials said.

The local government described it as a "violent terrorist attack" but said the situation was now under control.

China's President Xi Jinping, who has just visited the region, has promised to step up "anti-terrorism" efforts.

President Xi urged "'decisive actions' against violent terrorist attacks" following the incident, Xinhua news agency said.

Verifying reports from the region is difficult because the flow of information out of Xinjiang is tightly controlled.

Xinjiang has seen a series of violent attacks in the past year. Beijing blames the violence on separatists from the mainly Muslim Uighur minority.

Image copyright AP Image caption Dozens were injured in the fatal blast that took place as a train from Chengdu arrived

'Debris and suitcases'

"At around 19:10 on 30 April, an explosion happened at the passenger exit of Urumqi South Station when Train K453 from Chengdu to Urumqi arrived at the station, causing casualties," Xinjiang's local government news portal said.

"According to initial police investigations... the attackers used knives to stab people at the station exit, and detonated explosives at the same time," it said, adding that all the injured were receiving medical treatment.

Witnesses told Xinhua news agency that the explosion appeared to be centred around luggage left on the ground between a station exit and a bus stop.

Photos on social media, which could not be independently verified, appeared to show suitcases and debris strewn across a street after the blast.

Image copyright AP Image caption The explosion took place near a passenger exit, officials said

Image copyright AP Image caption During his visit to Xinjiang, Xi Jinping vowed a "strike first" approach to security

However, several microblog posts and photos related to the explosion appeared to have been quickly deleted from Sina Weibo, China's largest microblog platform.

The station was closed after the incident and services suspended but it has since been reopened.

Luo Fuyong, a spokesman for the regional government, told Reuters news agency the situation was "well under control".

"The wounded are receiving medical attention," he said.

The government was assessing casualties and the cause of the explosion, Mr Luo added.

The station was scheduled to launch three new intercity railway lines linking Urumqi with three other cities in Xinjiang on Thursday, Xinhua said.

The blast also came as Xi Jinping completed a visit to Xinjiang - the first since he became president in 2012.

Uighurs and Xinjiang Uighurs are ethnically Turkic Muslims

They make up about 45% of the region's population; 40% are Han Chinese

China re-established control in 1949 after crushing short-lived state of East Turkestan

Since then, there has been large-scale immigration of Han Chinese

Uighurs fear erosion of traditional culture Q&A: China and the Uighurs

During the visit, Xinhua news agency said Mr Xi had vowed to deploy a "strike-first approach against terrorists in the region", and said the province's long-term stability was "vital to the whole country's reform, development and stability".

Xinjiang has witnessed serious ethnic tensions in recent years, the BBC's Martin Patience in Beijing reports.

The region's Uighur Muslim minority, who number around nine million, have long complained of repression under Chinese rule - an accusation Beijing denies, our correspondent adds.

In March, Chinese officials blamed separatists from the Xinjiang region for a mass knife attack in Kunming, south-west China, which killed 29 and left more than 130 injured.

"We have seen attacks and problems in Urumqi before, but we haven't seen anything on this scale in quite a while," said Raffaello Pantucci, a senior research fellow with the military think tank the Royal United Services Institute (Rusi).

"I think the issue is that the problem [of attacks] in Xinjiang is getting worse," he told the BBC, adding that he believed incidents were becoming more professional and aimed at larger targets.