In a Sunday message to his Tajik counterpart, Emomali Rahmon, Rouhani congratulated the Central Asian nation on the 27th anniversary of its independence from the Soviet Union that collapsed in 1991.
He also expressed confidence that Tehran and Dushanbe will enhance relations to serve their mutual interests and strengthen regional security and stability.
In a separate letter to leader of North Korea Kim Jong-un, the Iranian president congratulated the East Asian nation on the 70th anniversary of the country's founding.
Rouhani also wished for growing links between Iran and North Korea in various fields.
North Korea is marking its 70th founding anniversary on Sunday, as its capital Pyongyang is holding elaborate celebrations with many foreigners in attendance.
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