Ohio State University sent a tweet to students warning them to "Run Hide Fight".

Hours later police declared the scene "secure" lifting the shelter-in-place order and cancelling classes for the remainder of Monday.

Columbus Fire Department said two casualties were stable, but the conditions of five others are unclear.

US media are reporting that nine people were injured in the attack at the Columbus-based university, which has 60,000 students.

Students barricade a classroom door amid campus lockdown at Ohio State UniversityABC
Students barricade a classroom door amid the campus lockdown at Ohio State University
Local media reported earlier that police would need time and manpower to secure the campus, which is one of the largest in the US.

Columbus Police tweeted that they had sent a SWAT team, dog units, negotiators and a helicopter to the scene.

Federal officials from the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives also responded.

The shooting began around 10:00 local time near Watts Hall, the college`s materials science and engineering building.

"The first thing I heard were screams," student Cydney Ireland told ABC News.

"Probably five seconds after that there were three gunshots and it sounded like a handgun.

"And I`ve never seen anything like it. Everybody was running in any direction they possibly could."

According to the school newspaper, The Lantern, police have surrounded the Lane Avenue parking garage, where an officer at the scene said a suspected shooter was believed to be inside.

A bomb squad was also at the scene, the newspaper reported.

Nearby public school districts also placed their students on lockdown.

No students will be able to leave the Upper Arlington or Grandview schools without a parent or guardian.

"Ohio`s thoughts and prayers go out to the Ohio State community," Ohio Governor John Kasich tweeted.

"Be safe, listen to first responders", he added.

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