BRUSSELS — NATO Secretary-General Jens Stoltenberg said Thursday that Russia has launched war on Ukraine and shattered peace on the European continent.

Stoltenberg called for a summit of NATO leaders for Friday. He spoke shortly after the trans-Atlantic alliance agreed after emergency talks to further beef up its land, sea and air forces on its eastern flank near Ukraine and Russia.

“Russia has attacked Ukraine,” Stoltenberg said. “This is a brutal act of war. Our thoughts are with the brave people of Ukraine.”

“Peace on our continent has been shattered,” he said. “This is a deliberate, cold-blooded and long-planned invasion. Russia is using force to try to rewrite history.”

Russia launched a wide-ranging attack on Ukraine on Thursday, hitting cities and bases with airstrikes or shelling. Ukraine’s government said Russian tanks and troops rolled across the border and accused Moscow of unleashing a “full-scale war.”

NATO emergency meeting came after countries closest to the conflict — Estonia, Latvia, Lithuania and Poland — requested rare consultations under Article 4 of NATO’s founding treaty, which can be launched when “the territorial integrity, political independence or security of any of the (NATO) parties is threatened.”

“We have decided, in line with our defensive planning to protect all allies, to take additional steps to further strengthen deterrence and defense across the Alliance,” the envoys said. “Our measures are and remain preventive, proportionate and non-escalatory.”

Lithuania declared a state of emergency in a decree signed by President Gitanas Nauseda in response to Russia’s attack. The Baltic country’s parliament was expected to approve the measure in an extraordinary session later Thursday.

The measure, in effect until March 10, allows for a more flexible use of state reserve funds and increased border protection, giving border guards greater authorities to stop and search individuals and vehicles in border areas.

NATO member Lithuania borders Russia’s Kaliningrad region to the southwest, Belarus to the east, Latvia to the north and Poland to the south.

While some of NATO’s 30 member countries are supplying arms, ammunition and other equipment to Ukraine, NATO as an organization isn’t. It won’t launch any military action in support of Ukraine, which is a close partner but has no prospect of joining.

Estonia, Latvia and Lithuania, however, said in a joint statement: “We would need to urgently provide Ukrainian people with weapons, ammunition and any other kind of military support to defend itself as well as economic, financial and political assistance and support, humanitarian aid.”

“The most effective response to Russia’s aggression is unity,” Estonian Prime Minister Kaja Kallas tweeted. “Russia’s widespread aggression is a threat to the entire world and to all NATO countries.”

Kallas called for measures “for ensuring the defense of NATO Allies.”

NATO began beefing up its defenses in northeastern Europe after Russia annexed Ukraine’s Crimean Peninsula in 2014. It has around 5,000 troops and equipment stationed there, but those forces have been beefed up with troops and equipment from several countries in recent months.

A first step now could be to activate the NATO Response Force, which can number up to 40,000 troops. A quickly deployable land brigade that is part of the NRF — made up of around 5,000 troops and run by France alongside Germany, Poland, Portugal and Spain — is already on heightened alert.

Some NATO members have also sent troops, aircraft and warships to the Black Sea region, near allies Bulgaria, Romania and Turkey. The Pentagon has also put up to 8,500 U.S. troops on heightened alert, so they will be prepared to deploy if needed to reassure other allies.

Jan M. Olsen in Copenhagen, Denmark, contributed to this report.