Parliamentary Speaker Kadri Veseli had invited the opposition to take part in the debate on Thursday on the EU-brokered deal with Serbia to "together express our reservations or displeasure or support for the Brussels agreement."
But Albin Kurti, leader of the opposition Self-Determination Party, triggered a device described as a gas canister and then started kicking it around the chamber to spread the smoke. Two politicians were taken to hospital and four ambulances outside the building were seen offering first aid to those affected.
Kurti is a former student leader who protested against Serbian rule in the 1990s. "No one has the mandate or the right to bring Serbia back into Kosovo," an opposition bloc Kurti is part of said in a statement. "We will not let this happen."
Opposition politicians had previously blown whistles and thrown eggs to show their displeasure with the deal that would give more power to Kosovo's Serb-majority areas.
A government statement later said the opposition's "violent behavior" had "exceeded all bounds of institutional and democratic behavior."
Kosovo's President Atifete Jahjaga denounced the "nasty actions of the opposition's lawmakers."
Prime Minister Isa Mustafa's Democratic Party and Foreign Minister Hashim Thaci's Democratic League of Kosovo hold 68 of the 120 parliamentary seats.
Glauk Konjufca of the Self-Determination Party said the protests at the weekly sessions on Thursdays would continue: "(We are) blocking parliamentary life in Kosovo to reject what the government signed and we ask the government to withdraw its signature from the recent agreements with Serbia, especially this about the establishment of the Serbian association of municipalities," he said.
In a deal brokered by the EU in August, Kosovo agreed to give more financial and legislative rights to its minority Serb community via an Association of Serb Municipalities. Kosovo has a predominantly ethnic Albanian population.
Kosovo declared independence from Serbia in 2008. The government in Belgrade rejected the move and still considers Kosovo as a southern province of Serbia. Kosovo's independence has been recognized by more than 100 countries, but Serbia and its ally Russia have collaborated to prevent its accession to the United Nations.
Kosovo and Serbia went to war in 1998-1999. Serbian armed forces withdrew from the territory after an 11-week NATO bombing campaign.
jm/sms (Reuters, AFP)