Russian President Vladimir Putin on Saturday insisted that the residents of four Ukrainian regions that Moscow illegally annexed a year ago “made their choice — to be with their Fatherland.”

In an address released in the early hours to mark the first anniversary of the annexation, Putin insisted that it was carried out “in full accordance with international norms.”

He also claimed that residents of the Donetsk, Luhansk, Zaporizhzhia and Kherson regions had again expressed their desire to be part of Russia in local elections earlier this month, in which Russia's Central Election Commission said that the country's ruling party won the most votes.

The West has denounced both the referendum votes carried out last year and the recent ballots as a sham.

The votes were held as Russian authorities attempted to tighten their grip on territories Moscow illegally annexed a year ago and still does not fully control.

A concert was held in Red Square on Friday to mark the anniversary, but Putin did not participate.

Meanwhile, in Ukraine, air defences shot down 30 out of 40 Iranian-made kamikaze drones aimed at the Odesa, Mykolaiv and Vinnytsia provinces overnight, the Ukrainian air force said Saturday.

Vinnytsia regional Gov. Serhii Borzov said that air defences shot down 20 drones over his central Ukrainian region, but that a “powerful fire” broke out in the town of Kalynivka when a drone struck an unspecified infrastructure facility.

Romania's Ministry of National Defence said on Saturday that a possible unauthorised entry into its national airspace occurred overnight amid the bombardment.

It said the radar surveillance system of the Romanian Army detected “a possible unauthorised entry” into the national airspace of NATO member Romania, with a signal detected toward the city of Galati, which is close to the border with Ukraine.

“At this moment, no objects have been identified that fell from the airspace onto the national territory,” the statement read, adding that NATO allies were informed in real time and that searches will continue through Saturday.

Emergency authorities issued text message alerts overnight to residents living in the counties of Galati and Tulcea, after detecting what the defence ministry said was “groups of drones heading toward Ukrainian territory” near the border.

In recent weeks, Romania has found drone fragments on its soil from the war next door at least three times as Russian forces carry out sustained attacks on Ukraine's Danube ports.

Russia's Defence Ministry said Saturday that it had shot down nine Ukrainian rockets fired at its southern Belgorod region, which borders Ukraine.

Local officials in Russia's Bryansk region, also bordering Ukraine, reported disruptions to power supply following an unspecified attack on the town of Pogar.

Drone strikes and shelling in the Russian border regions are a regular occurrence.