NATO allies plan to send patrol aircraft and missiles to strengthen Ankara"s air defenses on its border with Syria, officials said on Tuesday, following Turkey"s shooting-down of a Russian bomber.

As NATO countries seek to reassure Ankara over the fallout of Russia"s incursions into its air space, a decision by Germany and the United States to remove their Patriot missile batteries from Turkey left other allies to fill the gap.

Foreign ministers said in a statement that the situation on Turkey"s border with Syria and Iraq was "highly unstable" and committed to increase Turkey"s air defenses, which they described as "assurance measures".

"We remain determined ... to continue developing additional NATO assurance measures and allies are working to prepare other possible contributions," ministers said.

NATO Secretary-General Jens Stoltenberg said he expected a decision on a package "within weeks" but sought to portray the reinforcements as separate from Russia"s air incursions and called for Russia and Turkey to seek a solution to the tensions.