"I am astonished by the scope of the concerns but take them seriously," Pahor told a joint news conference with Lithuania's President Dalia Grybauskaite when asked about the Zapad 2017 military exercise to take place in Russia and Belarus this fall.
Grybauskaite said she had informed her Slovenian counterpart during the meeting about the offensive character of the future training, which is targeted against the Western world.
Historically, Slovenia has friendly relations with Moscow, although it has joined the European Union's (EU) sanctions against Russia over annexation of Crimea and support to separatists in eastern Ukraine.
Pahor said he could understand that the security situation in Europe had changed significantly over the past years.
"Who would have thought ten years ago that we would face annexation of Crimea? Who would have thought that instability in Ukraine would be as immense, as it is now? Who would have thought that Caucasus would face such big problems and who would have thought of the political and military crisis, which is so crucial for the European Union, we would face in the Middle East?," the Slovenian president said.
"Therefore, it is important for Slovenia to listen to its friends, listen to the Lithuanian president and maintain security and peace," he added.
Cyber security was also on the agenda of the Monday's meeting between the presidents of Lithuania and Slovenia.
On Tuesday, the two leaders will be escorted to the National Cyber Security Center that is in charge of safety of state information systems and their infrastructure.