Six NATO hubs being established along the alliance's eastern flank went into operation on September 1, the alliance said, in a move responding to a perceived new security threat from Russia.

NATO has been stepping up its role in Eastern Europe to deter potential aggressors and reassure its allies in light of the conflict in Ukraine, where Russia has been condemned for annexing Crimea and backing pro-Moscow separatists.

The six NATO centers -- in Bulgaria, Estonia, Latvia, Lithuania, Poland, and Romania -- are to help on the ground with exercises and planning activities. Each should be staffed with around 40 people by the end of the year.

"They have begun work, but are not yet operating at full capacity," a NATO spokesman said.

NATO Secretary-General Jens Stoltenberg is due on September 3 to attend an inauguration ceremony at the Lithuanian command-and-control center.

The decision to establish the so-called NATO Force Integration Units was made at the alliance's Wales summit in September 2014. They are to be fully operational by the next NATO summit, taking place in Warsaw in July 2016, the spokesman said.

Based on reporting by dpa and AFP