Six people were wounded in a knife attack at a Chinese train station Tuesday, the third in a series of recent station stabbings with authorities blaming the first two on "terrorists" from Xinjiang.

Police shot one of the attackers at the station in the southern metropolis of Guangzhou, the city's public security bureau said in a statement on its microblog, adding that all six injured had been hospitalised.

Four attackers were involved, the People's Daily newspaper reported on its verified microblog, adding they were wearing white caps -- often donned by Muslims -- and police opened fire on them after they ignored warnings.

Reports said one of the men died, one was arrested and two escaped, with one of them captured later.

The incident comes less than a week after a stabbing spree and explosion at the opposite end of the country left two attackers and a civilian dead, and 79 people wounded, at a railway station in Urumqi.

The city is the capital of Xinjiang, home to the mostly Muslim Uighur minority.

Last week's blast came as President Xi Jinping was wrapping up an "inspection tour" of the volatile region, during which he called for a "strike-first" strategy to fight terrorism.

"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," Xi said in comments published last week by the official Xinhua news agency.

Tuesday's incident also follows a March attack at a train station in the southwestern city of Kunming. Machete-wielding attackers killed 29 people there and wounded 143 in what many in China have dubbed the country's "9/11".

Authorities blamed both the Kunming and Urumqi incidents on terrorists from Xinjiang whom they say are linked to overseas extremist networks.

Foreign ministry spokeswoman Hua Chunying declined to speculate on who was responsible for the Guangzhou attack.

"Whoever carried out this violent action and for whatever reason, they will be brought into justice because these are criminal acts," she told a regular briefing.

"China's government will take strong action to safeguard the life and property of Chinese people."

But Rohan Gunaratna, professor of security studies at Nanyang Technological University in Singapore, told AFP: "The scale of violence in Xinjiang has steadfastly increased and now it is spilling over to other parts of China.

"China faces now a very significant and a really sustained threat from terrorism," he told AFP.

- 'Machetes half a metre long' -

The attackers struck as a train arrived at the station from Kunming, the Guangzhou-based Southern Metropolis Daily reported.

It cited eyewitnesses as saying several young men wielding machetes "about half a metre long" and wearing white clothing and hats began slashing at the passengers as they left the station.

Photos of the aftermath of the attack circulated widely on Chinese social media sites, with many users expressing shock and outrage.

One image on Sina Weibo, a Chinese equivalent of Twitter, showed a man -- his shirt stained with blood -- being carried from the station by three men as passers-by watched.

Another showed a crowd of hundreds gathered outside the station's main square, which was cordoned off by police as emergency personnel loaded people into an ambulance.

"Guangzhou has become really unsafe!" one Weibo user wrote. "Next time I see someone wearing a white hat, I'm heading the other way."

Another user posted: "We have daily security checks, and the result is still that these kinds of incidents don't stop happening."

Mao Shoulong, a professor at the school of public administration and policy at Renmin University in Beijing, said authorities were likely to impose increased "vigilance" across the country.

"This is an important test for the government," he told AFP.

"It has to firmly crack down on terrorism while imposing policies" aimed at easing fears and suspicions of Uighurs, he added.

A senior US official denounced the stabbing.

"My reaction to the knife attack in Guangzhou is one of horror, outrage and sympathy," Daniel Russel, Assistant Secretary of State for East Asian and Pacific Affairs, told reporters in Hong Kong.

"We are appalled at the action and categorically condemn the attack against innocent civilians."

"I think I speak for all Americans in expressing heartfelt sympathy to the victims, their families and the people of China."

Mass violent incidents in China are rare but have been on the rise in recent months.

In October three family members from Xinjiang died when they drove a car into crowds of tourists at Beijing's Tiananmen Square, the symbolic heart of the Chinese state, killing two before the vehicle burst into flames.