Five people have been injured in a shooting at the private Northeastern American College in Monterrey, northern Mexico.

A student allegedly entered the school around 8am on Wednesday morning, waited until he got into class, and shot his teacher, 24, and three classmates aged between 14 and 15.

The suspect, reported as 15 years old, allegedly then shot himself.

Nuevo León state security spokesman Aldo Fasci said that three people were seriously injured, according to the Associated Press, and that the incident was "unprecedented".

Mr Fasci said that a video showed the student firing at the teacher and fellow students. He then pointed the gun towards other classmates before shooting himself.

"[This] is result of a situation that is happening everywhere. The children have access to the internet. This has happened in other countries," he said.

In the confusion of the aftermath, parents and staff gathered around the entrance to the college. Disturbing pictures showed one of the injured, bleeding, being carried into an ambulance.

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El Universal newspaper reported that the teenage shooter was taken to hospital in a serious condition.

There were conflicting reports that the injured had died, then the gunman's condition was downgraded to "critical". There was also mixed information on the age of the shooter, and how many people were injured.

School shootings in Mexico are extremely rare.