Investigators in Afghanistan are searching for an American and an Australian who were kidnapped in western Kabul, the city's police chief told CNN.

The two men, lecturers at the American University of Afghanistan, were kidnapped Sunday evening when two gunmen stopped the car they were riding in, an Afghan security official told CNN.

One assailant broke the passenger-side window with his gun and took the two men away. A driver and bodyguard were left unhurt, the official said. The kidnappers were wearing military uniforms, the official said, but not the design and color of the official Afghan army uniform.

There has been no claim of responsibility.

The US Embassy in Kabul confirmed that an American citizen had been kidnapped near the university.

Embassy security officials are working with Afghan law enforcement and the school to assist in the investigation into the kidnapping, embassy spokeswoman Susan C. Doman said.

Officials at the university could not be immediately be reached for comment.

On its Twitter account, the school describes itself as "Afghanistan's only private, independent and not-for-profit university."

The school said on its Facebook page that its Kabul campuses will remain closed Monday and Tuesday but did not explain why. Regional centers are operating as normal, the Facebook page said.

The incident comes after six tourists were injured in western Afghanistan Thursday when a rocket struck the vans they were traveling in. The Taliban claimed responsibility for that attack, which occurred in Herat province.

The tourists were from the United States, Ireland, Britain and Germany.

Many countries, including the US and UK, have longstanding travel advisories warning against all but essential travel to Afghanistan due to the security situation throughout the country.