The European Sky Shield initiative -- unveiled by German Chancellor Olaf Scholz in the summer -- will see the countries look to purchase advanced Patriot and Iris-T systems, German Defence Minister Christine Lambrecht said.

The group -- which includes the United Kingdom, Baltic states and NATO invitee Finland -- is also eyeing the potential purchase of the Israeli-American Arrow 3 system, Lambrecht said.

"These are threatening and challenging times," Lambrecht said after the signing of a "letter of intent" on the sidelines of a NATO meeting in Brussels.

"We need to fill these gaps quickly."

The push for a European air defence system comes as Russia continues to pound Ukraine with ferocious missile barrages almost eight months into its war on its pro-Western neighbour.

NATO allies are scrambling to get more air defence systems to Ukraine but have admitted that they have precious few advanced systems to spare.

The new units to be purchased under the German plan are intended to help protect the skies over NATO and officials said would not be given to Kyiv.

NATO Deputy Secretary General Mircea Geoana said the plan "is even more crucial today, as we witness the ruthless and indiscriminate missile attacks by Russia in Ukraine, killing civilians and destroying critical infrastructure".

"The new assets, fully interoperable and seamlessly integrated within the NATO air and missile defence, would significantly enhance our ability to defend the alliance from all air and missile threats."