A Romanian F-16 fighter jet has destroyed an explosive-laden maritime drone close to Europe's largest offshore gas project, hours after another drone entered the NATO member's airspace and crashed near the Ukrainian border.

Romania's President Nicuşor Dan blamed Russia for the latest incident and condemned what he called an escalation of "irresponsible incidents" by Moscow.

The maritime drone was spotted by a commercial vessel at 06:28 local time on Thursday, a few hundred metres from work at the Neptun Deep offshore gas project, around 80 nautical miles east of the Romanian city of Constanța.

Two Romanian F-16 fighter jets were scrambled and one destroyed the drone after authorities decided it posed a potential threat to the hundreds of people working at the site and to critical energy infrastructure.

Defence Minister Radu Miruță said the drone was carrying explosives and that Kyiv had confirmed it was not Ukrainian.