He had previously survived an assassination attempt by the Tamil Tigers when he represented the United National Party, now in the opposition.
Hospital director Hector Weerasinghe told reporters Maheshwaran's condition is critical.
The politician ran a business which provided shipping services to the northern Jaffna peninsula which the guerrillas are trying to isolate. . For updates on this story go to the news front page at www.lbo.lk or click this link.