Chinese state television on Tuesday broadcast an interview with a police officer said to have shot five knife-wielding thugs who killed and injured scores of people in a railway station attack in Kunming.

Security remained tight and residents were nervous in the southwestern city, four days after the assault that state media dubbed "China's 9/11".

Both Beijing and Washington have described the attack as terrorism, with China blaming separatists from its restive far-western region of Xinjiang -- home to the mainly Muslim Uighur minority -- for killing 29 people and injuring 143.

The unnamed officer, whose face was not shown, said it took him 15 seconds to shoot the five attackers -- four of them fatally -- during the assault.

He leads a four-member emergency response team that arrived at the scene 10 minutes after the stabbing started but was the only one equipped with an automatic rifle, he told state broadcaster China Central Television (CCTV).

"Some people were being held on the ground and they were still stabbing them," he said.

Five of the attackers turned towards him, he said, and he fired a warning shot but they did not respond.

He then shot at the one closest to him, who was "in black clothes and veiled (and) held a knife about 60-70 centimetres (24-27 inches)" long.

"The other four did not back off and continued to run at me, with knives," the police officer said in the interview. "I shot all of them.

"It probably took 15 seconds from firing the first shot to the moment when all five were shot and fell to the ground.".

Few further details were given by CCTV for what the team did between arriving at the station and the officer opening fire, or afterwards.

Some reports have said the entire incident lasted as long as 25 minutes. The discrepancy remains unexplained.

- 'I saved many civilians' -

"I think I saved many innocent civilians. I did right by the people of Kunming and I did right by using my gun," the policeman told CCTV.

Railway police officer Zhang Liyuan, who lost a finger in the assault, told state news agency Xinhua how he had chased the attackers.

"One of the attackers turned around and cut right on my hand," Zhang said, adding that two of his colleagues were stabbed in the head and abdomen.

The public security ministry said an eight-strong gang carried out the attack, with three other suspects captured Monday. Four assailants were shot dead at the scene and one injured woman was detained, it said.

The Communist Party head of Yunnan province said Tuesday that the woman had confessed, according to a news portal run by the national prosecuting authority.

Police maintained a prominent presence at Kunming station Tuesday, with two riot vans next to the main plaza in front of the scene of the attack.

Armed guards were also on watch at the airport's main entrances, and paramilitary police with riot shields patrolled the terminal building.

Police vans were parked at many of the city's major junctions and officers patrolled the ground floor of Kunming's Number One People's Hospital, where casualties were still being treated. Witnesses have described how the attackers aimed for their victims' heads and necks to achieve maximum casualties.

A memorial service for the victims was held in the city centre on Tuesday night, Xinhua said.

The EU presidency, held by Greece, on Tuesday condemned the stabbing spree as "terrorism".

"We express our deep sorrow for the dead and injured," Greek Foreign Minister Evangelos Venizelos told reporters.

- 'Not state enemies' -

Separately, the Munich-based World Uyghur Congress (WUC) strongly condemned the violence and its exiled president, Rebiya Kadeer, appealed to Beijing not to crack down on Uighurs.

"At this time of heightened tensions, it is important the Chinese government deal with the incident rationally and not set about demonising the Uighur people as state enemies," Kadeer said in a statement.

The vast and resource-rich region of Xinjiang has for years been hit by occasional unrest that authorities blame on the Uighurs, saying China faces a violent separatist movement in the area motivated by religious extremism and linked to foreign terrorist groups.

Rights groups say the tensions are driven by cultural oppression, intrusive security measures and an influx of majority Han Chinese, resulting in decades of discrimination and economic inequality. Beijing insists that its policies in the region have brought prosperity and higher living standards.

The WUC said in its statement that it "unequivocally condemns the violence" and also expressed condolences to the victims and their families.

Once a wealthy businesswoman, Kadeer fell out with the Chinese government and was jailed before being released in 2005 and moving to the United States, where she is based.

Foreign ministry spokesman Qin Gang dismissed the WUC as "an anti-China separatist organisation" that was "not qualified to represent Uighurs in China".