A British surveillance drone belonging to NATO performed flights over Romanian airspace on Tuesday as part of an exercise aimed at raising patrolling levels near the border with Ukraine, the Romanian Defence Ministry said.

AWACS (airborne early warning and control) planes fly at an altitude of 9,000 metres, and their radars can survey an area of up to 312,000 square kilometres.

Similar monitoring flights have started in Poland, which also shares a border with Ukraine.

The Atlantic alliance on Monday to employ NATO AWACS surveillance aircraft over Poland and Romania in order to enhance awareness of what is happening in the region, including Ukraine, and reassure NATO states in the region.

Russia’s intervention in Ukraine’s Crimean peninsula has alarmed neighboring countries, including alliance members that used to be dominated by the Soviet Union.

NATO member Romania is one of the alliance’s strongest supporters among the ex-Communist countries of Eastern Europe.

In related development, Romania risked courting Russian displeasure on Monday when it signed an agreement boosting military and other forms of cooperation with Ukraine – whose new government Russia refuses to recognise.

Romania, which has a 694km-long border with Ukraine, has recognized the new authorities in Kiev as a legitimate government and has asked Russia to pull its forces out of Crimea.

At the same time, Romania has asked Ukraine to respect the rights of national minorities, including the Romanian minority.