Four female students who appeared in a viral video of an assault on two young girls in Sichuan province have been forced to apologize and their families ordered to pay compensation, police said on Wednesday.

The group - identified as Li, Liu and Zhao, all 14, and Zhang, 13 - were taken into custody after an investigation into footage filmed on Friday that showed the victims being repeatedly slapped and kicked.

According to the local authorities, the video was recorded outside a high school attended by the victims in Longfeng town, which forms part of Pengzhou. The suspects attend other schools in the area.

The city's public security bureau said on Wednesday that the suspects' families had been fined an undisclosed sum and ordered to cover any medical expenses. All of the suspects were placed in administrative detention, except for Zhang, as children under the age of 14 cannot be detained.

The victims had accepted the girls' apologies, the bureau added.

Lasting just over two minutes, the video shows a girl dressed in black who first slaps a young student in a green school uniform 14 times within 35 seconds, and then kicks and hits a short-haired girl. Neither victim is seen fighting back.

Police did not reveal which of the suspects was the girl in black or the motivation behind the assault.

The incident is the latest in a string of bullying cases that have gained media attention in the past year.

On April 22, a video showed a female student in Hunan province being slapped 32 times by a group of female students in less than 100 minutes.

On May 16, a male high school student in Shandong province was beaten by another boy in a school toilet.

Officials approved the arrest of 1,180 people involved in school bullying and violence nationwide last year, according to the Supreme People's Procuratorate, the top prosecuting authority.

A total of 688 first-time juvenile offenders or those who committed minor offenses were exempt from prosecution in the hope they would return to society a better person.

School violence has aroused widespread concern. The National People's Congress, the top legislature, announced in March that it will conduct an inspection of school safety this year and study how to reduce violence on campuses.

huangzhiling@chinadaily.com.cn