Tank and artillery were allegedly used by Russian-backed forces despite pledges to halt hostilities at midnight.
Kiev's military intelligence posted photos of the man's Russian ID.
Investigative group Bellingcat report "thousands of Russian servicemen" active in eastern Ukraine.
The first day of school is a day of celebration in Ukraine.
Kiev estimates tanks in rebel areas increased from 30 to 600 since 2014.
East Ukraine has seen an uptick in violence and casualties in recent weeks.
Six were also injured as the situation in the east grows more volatile.
The Kremlin has consistently used acts of terrorism as pretexts for the state of emergency Russia has been living under throughout the Putin years.
International community was "not tough enough" on Moscow.
Ukraine's representative in peace talks said rebels also have extensive artillery.
Will corruption and fraud, which has been an enduring characteristic of elections since Ukraine's independence in 1991, dictate their outcome?
On Ukraine's front lines, those who speak out are under constant threat of retaliation from the militias in power.
Seven soldiers were killed and nine injured in eastern Ukraine, state officials report.
Over 30 armored vehicles were recorded crossing what appears to be Luhansk city.
Luhansk's governor says poor weather is stalling the project.
Military courses have been shortened to get more cadets into Ukraine's armed forces faster.
Uncle Sam appears as villainous Fasciston, while the patriarch looks suspiciously like Putin.
Petro Poroshenko says Russia continues to build bases and train rebels in Ukraine.
Nearly 8,000 people have been killed since last year in the violence in Ukraine.
Ukraine's president will visit eastern regions on Wednesday but has not responded to the invite.
22 Russian tanks, along with 800 Russian fighters, have crossed the border according to Kiev.
Despite Poroshenko's insistence that weaponry is being withdrawn from the frontline, tensions are still running high.
For Ukrainian civilians, the first two months of 2015 have been especially deadly.
The document discusses co-opting regions of east Ukraine before last year's Euromaidan uprising.