Police arrested the suspect, an unemployed man in his 50s whose family name is Zhou, on the spot after yesterday’s attack, local police said in a statement, adding that he was under investigation.

The wounds of the two Japanese are not life threatening, while the Chinese citizen who was the most critically wounded is still undergoing treatment, the statement added.

An official at the Japanese consulate in Shanghai had told Reuters yesterday that a Japanese woman and her pre-schooler had been waiting for the bus at a stop when they were attacked.

A Chinese woman was also wounded.

Today, China’s foreign ministry spokesman Mao Ning called the attack an “isolated incident” that could have happened in any country in the world.

China has seen a spate of similar knife attacks in recent months across the country.

Last week, a 54-year-old male suspect was arrested after a knife attack that wounded three people inside a subway station in Shanghai.

Two weeks ago, four American instructors from a small Iowa university were wounded in what appeared to be a random stabbing attack in northeastern Jilin province, prompting Beijing to promise it would take measures to ensure the safety of foreigners.

A 55-year-old local man was detained the same day.

In May, two people were killed and 21 wounded in a knife attack at a hospital in southwest Yunnan province, and a 40-year-old male was arrested.

The same month, a 45-year-old woman was arrested after a knife attack killed two people and wounded 10 in a primary school in Guixi city of Jiangxi province.