An Indian court jailed 13 Islamists on Friday over an attack on a professor whose hand was chopped off after being accused of blaspheming the Prophet Muhammad in an exam paper.

The group were handed jail terms ranging from three to eight years at a court in the southern state of Kerala after being convicted last week on charges including attempted murder and conspiracy.

T. J. Joseph, a lecturer at Kerala's Newman College, was attacked in June 2010 following an allegation that a Malayalam language question paper he had set for his students included derogatory remarks about Muhammad.

Joseph has denied the allegation of blasphemy, saying he lifted the question from a book approved by Newman College, which mainly caters for post-graduate students.

The attackers, followers of a radical Islamist group known as the Popular Front of India, dragged Joseph out of his car on his way home from Catholic mass before severing his wrist with a sword.

The attack caused widespread outrage in Kerala, a southern state with a large Catholic population. Prosecutors produced more than 300 witnesses before the court to establish their guilt.