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 stated that the incursion could not be a mistake - it was an obvious expansion of the war by Russia. Moscow has yet to comment on the Romanian claims.

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

In its statement, Romania's defence ministry detailed that the drone was detected when two F-16 jets were monitoring the border with Ukraine, following Russian air attacks on Ukrainian infrastructure on the Danube.

The drone was located 20km (12.4 miles) south-west of the village of Chilia Veche, before it vanished from radar. However, it did not fly over populated areas or pose imminent danger, according to the ministry.

The EU's foreign policy chief, Kaja Kallas, condemned the incident as another unacceptable breach of an EU member state's sovereignty.

Poland also addressed the issue, with Prime Minister Donald Tusk announcing that preventative operations of aviation - both Polish and allied - have begun in their airspace, along with the ground-based air defence systems being heightened to readiness.

Earlier this week, Russia's defence ministry claimed they had no plans to target facilities in Poland, while Belarus described the drone entry as accidental due to navigation system jamming.

The Czech Republic has also responded by sending a special operations helicopter unit to Poland, as part of NATO's eastern flank protection.

In light of the drone incursions, President Zelensky reiterated that the Russian military knows exactly where their drones are headed and stresses the need for harsher sanctions against Moscow.

US President Donald Trump commented on the airspace violations, stating he was prepared to impose tougher sanctions on Russia if NATO countries ceased purchasing Russian oil.

Since Russia's full-scale invasion of Ukraine in February 2022, its military operations have faced increasing scrutiny as they attempt to gain ground in the ongoing conflict.