A Summit of NATO members' heads of state and government begins on Friday, with issues such as security at NATO's eastern flank and relations with Russia being high on the agenda.

Member states will formally approve the deployment of four multinational battalions in Poland and the Baltics. Additionally, a proposal to set up a multinational brigade in Romania that will provide training on a rotational basis are also expected to be given the green light.

Cyber security will also be addressed, as well as the response to hybrid warfare and terror threats.

A declaration of partnership is to be signed between NATO and the EU with a focus on the fight against people smuggling in the Mediterranean and Aegean seas.

The summit officially at 13:00 local time.

Bulgaria's delegation is led by President Rosen Plevneliev. It also includes Defense Minister Nikolay Nenchev.

On Saturday, Plevleniev will take part in a joint session with partners to the Resolute Support Mission in Afghanistan.

A session of the NATO-Ukraine Commission has also been scheduled for Saturday. A "comprehensive package of assistance" to the country, already approved by NATO defense ministers, is expected to be confirmed.

Earlier this week, NATO Secretary General Jens Stoltenberg said the Alliance would work hard to carry out a NATO-Russia Council meeting following the summit, a prospect Moscow has welcomed in principle.

But Russian Foreign Ministry Spokersperson Maria Zakharova raised concerns over NATO's activity near its border.

Zakharova downplayed suggestions that Russia posed a "threat" to Eastern Europe and made clear the country would respond to NATO moves that raise tensions.