"It was a targeted operation involving no more than 3,000 commandoes in each case that was meant," the source of the outlet said.
It is noted that the first invasion took place in August 2014, when the Ukrainian army had made a great progress fighting against the pro-Russian terrorists. The Russian army have crossed the border then and engaged into battle against the Ukrainian forces near Ilovaisk.
The Russian troops illegally crossed the Ukrainian border for the second time in 2014 as well but did not participated in combats.
"It was a preventive deployment not to allow Kyiv's troops to disrupt the "elections" in the occupied territories," an unnamed Russian official said.
After that, the Russian troops were ordered to re-invade Ukraine in January 2015 when the negotiations in Minsk were underway. The Russian army attacked the Ukrainian positions in Debaltseve then. The battle was fierce but the Ukrainian forces eventually retreated.
The last time the Russian army invaded Ukraine last month. But, again, there were no clashes with the Ukrainian army this time.
"Kyiv gathered 90,000 troops in August and was ready to launch the offensive. We had no choice. But our presence worked as a deterrent. German Chancellor Angela Merkel also put pressure on Petro Poroshenko having persuaded him to put aside the offensive as it might result in major loses," the source told the outlet.
According to the unnamed official, there are about 60,000 militants in the so-called "DPR" and "LPR" today. Only two thirds of them are locals, 10,000 terrorists are citizens from other regions of Ukraine, and another 9,000 are Russian career soldiers.