"The school teachers told us that many children are suffering from stress, which was caused by the conflict," Alexander Hug, deputy chief monitor of the OSCE special monitoring mission to Ukraine, told reporters in Kiev.

Thousands of children are suffering psychological disorders as terrifying and life-threatening situations, such as shelling, fighting and dangers posed by mines and explosives used in the conflict, have become a commonplace in their daily lives, Hug said.

He added that their situation is exacerbating amid growing militarization of the country.

"Our monitors saw armed men who patrolled the playground in Gorlovka town, controlled by the so-called Donetsk Republic. Meanwhile, in other areas, it became a routine for some children to pass through a military checkpoint to get to school," Hug said.

According to the United Nations Children's Fund, about 1.7 million children were affected by the conflict in eastern Ukraine. At least 68 children were reportedly killed and 180 others injured as the result of hostilities, which started in April 2014.