Philippe, King of the Belgians visited Tallinn on Tuesday and was formally received by President Kersti Kaljulaid at Kadriorg Palace.
As a fellow NATO member with troops currently stationed in Estonia as part of the Enhanced Forward Presence (eFP) battle group, the two heads of state focussed on the alliance.
"Although the direct threat to some NATO member states is small, it is in everyone's interest to show the world that NATO is united and ensures its security jointly,'' said Ms Kaljulaid at the meeting, ERR's Estonian news reports.
''Our base at Tapa, as well as those in our allies in the Baltic States and Poland, where NATO troops serve, is a clear signal of this unity,'' the president continued.
Other topics discussed included cyber-security and hybrid threats, as well as challenges facing the European Parliament ahead of May's elections, it is reported.
King Philippe I, who acceded to the throne in 2013 following the abdication of his father, Albert II, is on an official, working visit to Estonia, and is to visit the e-Estonia showroom as well as Belgian troops serving at Tapa, east of Tallinn. He is accompanied by the Belgian foreign and defence minister Didier Reynders.
Around 300 Belgian troops, principally from the Chasseurs Ardennais mechanised infantry batallion, are based at Tapa as part of the British-led battle group. Belgian pilots were amongst the first to engage in air policing duties following Estonia's accession to NATO in 2004.
Editor: Andrew Whyte