Ukraine has tightened security measures on the borders with Belarus and Moldova's breakaway region of Transnistria, the Ukrinform news agency reported Tuesday.

"The security measures have been strengthened to prevent escalation in these areas," Andriy Demchenko, the spokesman of the State Border Guard Service of Ukraine, was quoted as saying.

There is a possibility of a military invasion from Belarus to Ukraine, Demchenko said.

The Ukrainian forces stand ready to repel all possible attacks, he added.