Four US college instructors teaching in China have been stabbed while visiting a busy public park, in a rare case of violent crime against foreigners in the powerful security state.

The educators from Cornell College, a private liberal arts college in Mount Vernon, Iowa, were wounded “in a serious incident” on Monday, while participating in a partnership program with Beihua University in the city of Jilin, in northeastern China, according to the college.

“We have been in contact with all four instructors and are assisting them during this time,” Cornell College President Jonathan Brand said in a statement, adding no students took part in the program.

Footage purportedly showing the aftermath of the daylight attack, which emerged on Chinese social media on Monday but was swiftly censored, showed two men and a woman lying on the ground covered in large blood stains, surrounded by onlookers.

They appeared conscious and were talking on their cell phones, the video showed.

CNN geolocated the video of the attack to Beishan Park, a popular green space in Jilin city center, less than half an hour’s drive from Beihua University. Monday was a public holiday in China.

China’s Foreign Ministry confirmed Tuesday that “four foreign teachers at Beihua University were attacked” while visiting Beishan Park in Jilin on Monday morning, adding they were immediately taken to hospital and did not suffer life-threatening injuries.

“The police initially determined that the case was an isolated incident and are currently under further investigation,” ministry spokesperson Lin Jian told a regular news conference.

Details of the attack, including the motive and the identity of the assailant or assailants, remained unclear on Tuesday.

Iowa state representative Adam Zabner told CNN his brother, David Zabner, was one of the victims of the stabbing.

Rep. Zabner said his brother, who was on his second visit to China with Cornell, is “doing well” and has “been stitched up and seems to be recovering,” after speaking to him on Tuesday morning Beijing time.