BRUSSELS - The race is on to find a successor for Nato secretary general Jens Stoltenberg who said he would become Norway's central bank chief in December.

The end of Stoltenberg's eight-year Nato mandate comes amid heightened tension with Russia.

Former British Prime Minister Theresa May, her Dutch counterpart Mark Rutte, Estonian Prime Miniter Kaja Kallas, and former EU foreign policy chief Federica Mogherini are among those previously cited in European media as possible candidates.