Mogherini also confirmed the bloc's commitment to finding a political solution to the ongoing conflict in eastern Ukraine in line with the Minsk agreements.

"We also remain committed to promoting a sustainable political solution to the conflict in eastern Ukraine in line with the founding principles of the OSCE ... We continue to call for full implementation of the Minsk agreements by all sides," the EU foreign policy chief added.

Mogherini also pointed out that the process must go with full respect of Ukraine’s sovereignty, independence, unity and territorial integrity.

On November 25, three ships of the Ukrainian Navy — Berdyansk, Nikopol, and Yany Kapu — breached the Russian border, entered Russian territorial waters that were temporarily closed, and began moving toward the Kerch Strait, which serves as an entrance into the Sea of Azov. The Ukrainian vessels and their crew were detained by Russia after failing to respond to a lawful demand to stop.

In response to the incident, Ukrainian President Petro Poroshenko signed the decree on the martial law in several Ukrainian regions located near the Russian border and the coasts of the Black Sea and the Sea of Azov.

Russian President Vladimir Putin has said that the incident was a provocation prepared in advance as a pretext to introduce martial law in Ukraine. Putin said the provocation could be linked to Poroshenko's low approval rating ahead of the presidential campaign set to start in late December.