Romania's president said on Wednesday that nine central and eastern European countries would press at a November 4 summit for a greater NATO presence in the region in response to increasing security threats from the "east and south".

The Romanian presidency said in a statement that NATO Deputy Secretary General Alexander Vershbow would represent the military alliance at the summit in Bucharest to be chaired by Iohannis and his Polish counterpart Andrzej Duda.

Bulgaria, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania and Slovakia are all slated to participate in the summit.

Iohannis had said the participants plan to call for measures to "strengthen the eastern border of NATO and the EU".

He also spoke of the threat from "the south" -- including turbulent Syria.

Russia's 2014 annexation of the Crimea peninsula from Ukraine and backing of a pro-Russian rebellion in Ukraine's east has rattled nerves in other West-leaning former Soviet republics.

Several countries in the region have demanded greater protection from NATO, including the establishment of permanent bases.

In August, the US launched the biggest allied airborne drills in Europe since the Cold War ended, with nearly 5,000 soldiers from 11 NATO allies taking part in four weeks of operations across Germany, Italy, Bulgaria and Romania.

NATO, a 28-country alliance led by the United States, defended the number of military exercises as a response to "growing Russian aggression" and refuted suggestions they were increasing, rather than decreasing, the threat of conflict in Europe.