Nationals of Balkan countries who went to fight in Syria and are now returning are among factors that could result in terror attacks in the Balkan Peninsula, Macedonia's President Gjorge Ivanov has said.

Inspecting border controls in Southern Macedonia, he has asserted that his country is ready for a new wave of migratory pressure.

Considering that at least 1000 people from the Balkans have gone to fight in Syria and that around sixty percent of these have returned, the possibility of terrorist attacks in the region should not be excluded.

"As the [Islamic State (IS) group] is losing territory on the battlegrounds in Syria, but also in Lybia, a vast share of these people try to return... or some [of them] who reached EU territory together with migrants might try to take such action," state-run news agency MIA quotes him as saying.

He has made clear police and intelligence services are "closely following" fighters who returned.

As of July 27 there are 86 such people in Macedonia, he has estimated.

His visit to the border regions come as Serbia and Bulgaria are considering moves to bolster security at their common border to prevent a flow of illegal migrants.

Wednesday's talks between Bulgarian and Serbian senior military officers followed the decision of Belgrade to set up joint army and police forces that would be deployed at the country's borders with Bulgaria and Macedonia.