Spain will send four combat aircraft and 130 troops to Bulgaria to carry out air patrol missions amid tensions over Ukraine, the Bulgarian Defense Ministry said, Reuters reports.

The first Spanish Eurofighters are expected to land in Bulgaria by the end of the week to protect the airspace along with the Bulgarian Air Force until the end of March.

The mission is implementing measures to ensure the security of NATO member countries on the eastern flank, the Defense Ministry said in a statement.

The Netherlands is expected to send two F-35 aircraft to Bulgaria in April and May to patrol the airspace.

Bulgaria, a member of NATO since 2004, plans to create a battle group of up to 1,000 troops under Bulgarian command and in close cooperation with NATO, which will also include soldiers from other allied countries.