The attack happened during a meeting being held at the house of an MP in the former LTTE stronghold Kilinochchi.
"At least four party MPs were attending the discussion held at the house of our MP S Sritharan. A group of people came carrying the national flag in one hand and stones and clubs in the other and attacked us," Suresh Premachandran, a TNA MP, said.
He, however, said while 13 people were injured, the MPs escaped unhurt. One attacker was handed over to the police, he added.