The parliament unanimously approved the extension, officials said.
Legislators from the Tamil National Alliance (TNA) protested the emergency and boycotted the debate on the tough laws.
The TNA, a proxy of the rebel Liberation Tigers of Tamil Eelam (LTTE), staged a sit-in protest outside the parliament chamber and did not vote.
The state of emergency was imposed shortly after the August 12 assassination of the then foreign minister Lakshman Kadirgamar by a suspected Tiger sniper.
The government accused Tiger rebels of carrying out the killing, a claim they rejected.
The LTTE had asked the government to lift the state of emergency saying it was adding pressure to an already tenuous ceasefire which peace broker Norway arranged and put in place from February 2002.
Diplomatic efforts to revive the truce remain deadlocked with over 200 people killed in the last month alone in violence linked to the island's Tamil separatist conflict.
Diplomatic efforts to revive the truce remain d