It quoted police as saying the suspect was under police guard at the main hospital in Colombo and that the alleged gunman was a resident of Gurunagar in the northern Jaffna peninsula.
Maheshwaran was shot as he attended a new year service in a Hindu temple in Kotahena, a northern suburb of the capital Colombo, with a high concentration of minority Tamils.
He was rushed to hospital in a critical condition but succumbed to his injuries soon after.
He had previously survived an assassination attempt by the Tamil Tigers when he represented the United National Party, now the main opposition.
The politician ran a business which provided shipping services to the northern Jaffna peninsula, which the guerrillas are trying to isolate after the government closed the land route.
Of late he had also been critical of t