"Russia's appalling cruelty has caused immense human suffering and massive displacements, disproportionately affecting women and children", a declaration from a summit in Madrid said.

NATO leaders have funnelled billions of dollars of arms to Ukraine and faced appeals from President Volodymyr Zelensky for more artillery.

Alliance chief Jens Stoltenberg announced a new joint package of non-lethal support including secure communications equipment and anti-drone systems.

The assistance will also extend to training Ukrainian forces to pivot to more modern Western weapons over the longer term.

"Ukraine can count on us for as long as it takes," Stoltenberg said.

The war in Ukraine has shaken the 30-nation alliance and forced it into the biggest overhaul of its defences since the end of the Cold War.

The summit agreed a new guiding blueprint for NATO that said Russia "is the most significant and direct threat to Allies' security and to peace and stability in the Euro-Atlantic area".

"We cannot discount the possibility of an attack against allies' sovereignty and territorial integrity," the document, updated for the first time since 2010, said.

In a bid to counter the menace from Russia, leaders agreed to bolster their forces in eastern Europe.

"Allies have committed to deploy additional robust in-place combat-ready forces on our eastern flank," the summit statement said.