OSLO - Norway's opposition Centre Party said on Friday it would join three left-wing parties in backing a no-confidence motion against Justice Minister Sylvi Listhaug, heightening the risk that the minority cabinet will fall.Last Friday Listhaug rocked Norway's traditionally consensual politics by accusing the opposition Labour Party - target of the country's worst peacetime massacre - of putting terrorists' rights before national security.On July 22, 2011, far-right extremist Anders Behring Breivik killed eight people in downtown Oslo with a car bomb and then shot dead 69 people, many of them teenagers, at a Labour party camp on Utoeya Island.On Facebook last week, Listhaug posted a photograph of masked people clad in military fatigues, black scarves and ammunition with the text: "Labour thinks terrorists' rights are more important than the nation's security. Like and Share".Her post coincided with the premiere in Oslo of "Utoeya July 22", a movie about Breivik's deadly rampage, though she later said she had no intention of linking the two.But her comments triggered a political storm, and she apologized in parliament on Thursday. Some opposition parties, however, said her gesture was not sincere enough."The role of justice minister is a special role. It is about preparing for emergencies and stopping hateful rhetoric. We want a peaceful justice minister," Centre Party leader Trygve Slagsvold Vedum told reporters.The dispute erupted after Labour voted against a Listhaug-sponsored bill allowing the state the right, without judicial review, to strip individuals suspected of terrorism or joining foreign militant groups of their Norwegian citizenship. Labour wanted the courts to make such rulings. The bill was defeated.The uproar underlines how Breivik's attacks, seen as the worst acts of violence committed in Norway since World War Two, are still touching a raw nerve in the affluent Nordic state nearly seven years on."It is a very special situation," political scientist Johannes Bergh told Reuters. "Usually a motion of no confidence is about issues between parliament and the government. This is about something that has happened on Facebook." The opposition Christian Democrats, now holding the key to a majority against Listhaug, said they would decide on Monday how to vote in parliament the following day.Their leader has accused Listhaug of wanting to be as populist as US President Donald Trump.The no-confidence motion was first introduced by the small left Red Party and backed by Labour and the Socialist Left. Unless Listhaug were to step down, and thus defuse the situation, her future will rest in Christian Democratic hands.Prime Minister Erna Solberg would then face the choice of letting Listhaug go, weakening the cabinet and risking a defection by her Progress coalition ally, or to decide that the whole government should resign.Norway's cabinet is composed of the centre-right Conservatives led by Solberg, the right-wing Progress Party led by Finance Minister Siv Jensen, and of which Listhaug is a member, and the centrist Liberal party.