All the 28 member states of NATO have ratified Montenegro's alliance accession protocol.

“NATO Accession Protocol has been ratified! Thanks to all allies and partners!” the Government of Montenegro tweeted.

In April, the Parliament of Montenegro voted for joining North Atlantic Treaty Organization: 46 deputies from 81 voted for adoption of the relevant bill.

The opposition did not take part in the voting, but held a protest near the parliament building.

Earlier this week, Montenegro's Prime Minister Dusko Markovic said that the country will officially become the 29th member of NATO on June 5.