Unidentified gunmen have shot dead a professor of Islam in southern Pakistan.

Police said two gunmen on a motorcycle fired at a car carrying Mohammad Shakil Auj in the port city of Karachi on September 18.

A colleague said Auj, the 54-year-old dean of the faculty of Islamic Studies at the University of Karachi, had recently received threats following complaints that his teaching was too liberal.

Following the attack, university students rallied on campus to demand better protection for teachers.

Auj was known for his unorthodox views -- for example that a Muslim woman could marry a non-Muslim man.

In 2012, he complained to police that colleagues had threatened him and sent him text messages accusing him of blasphemy, a crime carrying the death sentence in Pakistan.

Based on reporting by AFP and Reuters