HONG KONG — The 10 or so attackers, dressed in black and wearing cloth masks, arrived in front of Kunming Railway Station in south-west China on Saturday night and began slashing at employees and commuters, sometimes repeatedly plunging their long knives into people too stunned or slow to flee.

The assault in Kunming, the capital of Yunnan province — one of the worst of its kind in China in recent memory — was an alarming rebuff to the Chinese government’s vows to bring stability to the ethnically divided far-western region of Xinjiang, where it said the attackers came from.

President Xi Jinping called the perpetrators “terrorists” and the widespread public revulsion and fear unleashed by the attack is likely to shore up the Chinese government’s position that its pervasive security controls in Xinjiang are justified and that even tighter policies are justified there and elsewhere.

… “As a single incident, you can say that this is the most brutal, cruel incident we’ve seen from Xinjiang,” Professor Rohan Gunaratna, from Nanyang Technological University in Singapore, who studies terrorism in Asia, including China, said in a telephone interview.