The government in the southern Indian state of Kerala says a strike by junior doctors is illegal and it's threatening to take tough action against them.

The strike began four days ago after the arrest of junior doctors following an outbreak of violence in a hospital in Trivandrum.

The doctors allegedly kicked a patient after an argument and also attacked the patient's mother when she tried to intervene.

Nearly five hundred junior doctors have been suspended and the state government wants the Indian medical council to cancel their registration.