BRUSSELS, Belgium —  NATO diplomats and Russia's ambassador to the alliance pledged to remain united in the fight against terror Tuesday, condemning that attack on a Russian school that left more than 350 people dead.

NATO ambassadors met with Russia's ambassador to the alliance, Konstantin Totskiy (search), to show solidarity following "the outrageous terrorist attacks perpetrated against the people of the Russian Federation."

Recent attacks, including the downing of two civilian aircraft and a suicide bombing at a crowded metro station in Moscow, "pose a direct challenge to our common security and shared democratic values," the group said in a joint statement issued after the meeting.

The two sides said the "mass murder of innocent school children and other civilians in Beslan ... underscore the barbaric and insidious nature of the terrorist threat we all face today."

The meeting held behind closed doors at NATO (search) headquarters was also used by allies to express their condolences to the Russian envoy, officials said.

The two sides said they "stand united in their categorical rejection of terrorism in all its manifestations." The attacks required "urgent and wide mobilization of all nations in combating this scourge."

NATO and Russia said they "remain determined to strengthen and intensify their common efforts" to fight terrorist groups, including drawing up an "action plan" by which both Moscow and the Brussels-based alliance could cooperate better.