NATO welcomed its 13th secretary general on Wednesday. Jens Stoltenberg, a former two-term prime minister of Norway known for consensus building, succeeds Anders Fogh Rasmussen, who had been the alliance's top civilian leader since 2009.

Ahead of taking up the five-year post, Stoltenberg emphasized that he would work to uphold the values that unite NATO's 28 member states.

"As we all know, NATO is not just a security alliance. It is a family of values which reaches across the Atlantic and defends almost 1 billion citizens of our allied countries," Stoltenberg said during a news conference at the NATO summit in Wales in early September.

"We must continue to stand up for those values," he said.

The defense readiness of NATO's members has become a major issue this year amid armed conflicts. Not only has fighting in North Africa and Syria put bordering member states – including Turkey - on alert, but also the armed conflict in Ukraine.

Russian President Vladimir Putin alarmed eastern European countries earlier this year when he backed the secession of Crimea with armed soldiers, later vowing to reunite the lost lands of the former Soviet Union. Poland and the Baltic states, in particular, have called on NATO for assistance to counter Russian aggression.

Stoltenberg is the first NATO chief to hail from a country which shares a border with Russia.

Former Secretary-General Rasmussen had intended to end his term at the end of July. However, the escalating conflicts prompted him to remain in office until after the NATO summit in Wales earlier last month.

kms/mz (AP, AFP, dpa)