Romania says a Russian drone has breached its airspace - the second NATO country to report such an incursion.

Romanian fighter jets were in the air monitoring a Russian attack in Ukraine on Saturday and were able to track the drone near Ukraine's southern border, the defence ministry said in a statement.

Ukrainian President Volodymyr Zelensky said the incursion could not be a mistake - it was 'an obvious expansion of the war by Russia'. Moscow has not commented on the Romanian claims.

On Wednesday, Poland said it had shot down at least three Russian drones which had entered its airspace.

In its statement, Romania's defence ministry said it detected the Russian drone when two F-16 jets were monitoring the country's border with Ukraine, after 'Russian air attacks on Ukrainian infrastructure on the Danube'.

The drone was detected 20km (12.4 miles) south-west of the village of Chilia Veche, before disappearing from the radar.

But it did not fly over populated areas or pose imminent danger, the ministry said.

Poland also responded to concerns over Russian drones on Saturday.

Preventative operations of aviation - Polish and allied - have begun in our airspace, Prime Minister Donald Tusk said in a post on X.

Earlier this week, Russia's defence ministry stated there had been 'no plans' to target facilities on Polish soil.

Belarus, a close Russian ally, claimed the drones that entered Polish airspace on Wednesday were an accident due to navigation systems being jammed.

This unfolding scenario raises alarm bells not only for Romania and Poland but also for NATO as a whole, reinforcing the need for vigilance amidst rising tensions in Eastern Europe.