"Forty years ago, we were forced to look at the world standing behind NATO's protective shield as something desirable and unattainable. In 2004, when we, along with several co-labourers in the same fate became members of both NATO and the European Union, there was a great moment of unification," Mr Ratas said on Friday.

"Hoisting the NATO flag in his yard on this day 15 years ago, [then-president] Lennart Meri said that Estonia would never be alone again. These words are true. This is confirmed by the daily support of our allies to our independence. Over the last five years alone, nearly 10,000 allied soldiers have been stationed in Estonia," the prime minister added.

Coincidentally, Friday also marks what would have been Lennart Meri's 90th birthday. President Meri died in 2006.

Defence minister Jüri Luik (Isamaa) noted on Friday that Article 5 of the NATO treaty has given Estonia the world's most powerful security guarantee, whereby an attack on one represents an attack on all.

"Our membership was achieved via years of hard work by politicians and state officials. When the NATO door was momentarily opened we were 100% ready for membership," he said.

"In light of acts of aggression by Russia, it is not difficult to imagine what would happen to us if we were not in NATO," Mr Luik added.

NATO decided to place Enhanced Foward Presence (eFP) battle groups in Estonia, Latvia, Lithuania and Poland, at the Warsaw Summit in 2016. This came following the 2014 annexation of Crimea by the Russian Federation, and the ongoing conflict in the Donbass region of eastern Ukraine, which began in the same year.

Estonia's eFP battle group, based at Tapa, east of Tallinn, is UK-led, and French, Danish and Belgian troops have also made up its numbers since it became reality in 2017.

Kalev sports hall event

Air policing duties are carried out from the Ämari air base west of Tallinn, with contributing NATO members having included Spain, Germany and Italy.

An image of the NATO flag is set to be projected on to the Stenbock House, the seat of government in Tallinn, from Friday until the following Thursday, to mark the anniversary.

In addition, the Estonian Atlantic Treaty Association in cooperation with NATO headquarters, the Ministry of Defence, the Ministry of Foreign Affairs and the Ministry of Education and Research, is to hold a public charity event at the Kalev Sports Hall in Tallinn on Friday afternoon. 

Prime Minister Jüri Ratas is set to make an opening address, followed by statements from outgoing Minister of Foreign Affairs Sven Mikser (SDE), secretary general of the defence ministry Kristjan Prikk, NATO HQ public diplomacy department program officer Eric Povel, and chief of staff of the volunteer Defence Leage (Kaitseliit) HQ Col Jaak Mee.

Founded in 1949, NATO is also celebrating its 75th anniversary this year, and consists of 29 members today. A recent opinion poll shows 76% of Estonian residents support membership of the alliance.