Sharjah24 - AFP: Tuesday, just before Kyiv is scheduled to launch a counteroffensive, an explosive device derailed a Russian goods train in an area bordering Ukraine for a second consecutive day.

Russian territory and Crimea, annexed by Moscow in 2014, have been hit in recent days by a series of attacks.

The last four days have seen two trains derailed by explosions, a suspected drone hitting an oil depot in Crimea that caused a huge blaze and power lines blown up near Saint Petersburg.

The strikes come as Russia gears up to celebrate May 9, a holiday marking the Soviet victory over the Nazis that has become a central event during President Vladimir Putin's rule.

Ukraine has followed its usual line of not claiming responsibility for the attacks, which came as Kyiv said it is finalising preparations for a spring offensive announced weeks ago.

Alexander Bogomaz, the governor of Russia's western Bryansk region, said Tuesday the train was derailed by an "unidentified explosive device."

He said it went off at Snezhetskaya station, outside the regional hub of Bryansk, a city of around 370,000 people near the Ukraine and Belarus borders.

"A locomotive and several wagons of the train derailed," he said, adding that there were no casualties.

On Monday, a similar explosion caused a train to derail and catch fire near Unecha, in the same region but closer to the Ukraine border.

Throughout its more than year-long offensive, the Kremlin has sought to portray Russia as safe while its troops fight in Ukraine.

Earlier on Tuesday it acknowledged a security threat.

"Of course, we are aware that the Kyiv regime, which is behind a number of such attacks -- terrorist attacks -- plans to continue this line," Kremlin spokesman Dmitry Peskov said.

"All our intelligence services are doing everything necessary to ensure security."