Afrasheem Ali of the Progressive Party of Maldives was attacked late Monday and police had one suspect in custody, The Wall Street Journal reported.
The incident is likely to further destabilize the Indian Ocean archipelago, where former Maldives President Mohamed Nasheed is on trial on abuse of power charges, political observers said.
Nasheed is accused of the unconstitutional arrest and detention of the chief criminal court judge, which led to widespread protests, a loss of support and his eventual resignation.
Nasheed skipped the first day of his trial Monday and left the capital to campaign for elections scheduled for next year.
The Maldives is a popular tourist destination.