Djukanovic's Democratic Party of Socialists has named his deputy, Dusko Markovic, as a possible premier-designate.

Djukanovic, who led the tiny Adriatic nation to independence from Serbia in 2006, has resigned twice in the past, but returned as either prime minister or president.

Djukanovic was 29 when he became the youngest prime minister in Europe in 1991. He was elected Montenegro president in 1998, before again assuming the premier's job in 2002. He is the longest serving Balkan leader.

The DPS won most seats in the October 16 parliamentary election, but will need to seek a coalition to remain in power.

The ruling party did not give a reason for his stepping-down.