In what may seem as more threat than warning, Russian President Vladimir Putin said that it is best not to "mess with" Russia as it is one of the leading nuclear powers.

The statement was made during an appearance at a pro-Kremlin youth camp on the banks of Lake Seliger near Moscow. "Thank God, I think no one is thinking of unleashing a large-scale conflict with Russia. I want to remind you that Russia is one of the leading nuclear powers," Putin told a group of Russian youngsters.

Ukraine and the West have accused Russia of invading Ukraine and supporting the separatists by sending troops and armour. However, Russia has maintained its innocence in the act.

Speaking at the assembly, Putin justified his stand in taking over of Crimea in March. He said that it was important to do that in order to protect the large Russian-speaking population from Ukrainian government violence. Moreover, the pro-Russian separatists uprising and fighting in eastern Ukraine was an outcome of a refusal by Kiev to negotiate, he said , reports Reuters.

"Russia is far from being involved in any large-scale conflicts," he said adding, "We don't want that and don't plan on it. But naturally, we should always be ready to repel any aggression towards Russia. I want to remind you that Russia is one of the leading nuclear powers."

The comments come a day before of gathering of European governments for an emergency summit to discuss further sanctions on Moscow.

The Telegraph has said that Putin's statements is couched in "language not seen since the height of the Cold War." It further reports a major battle is expected in the Ukrainian port city of Mariupol in the coming days. Ukrainian forces have dug up trenches awaiting a full-scale assault by rebels backed by Kremlin's forces.