The deal -- signed in Bishek by Kyrgyz President Sadyr Japarov and his Tajik counterpart Emomali Rakhmon -- is a sign of how relations between the two allies of Russia have improved since their last clash in autumn 2022.

"From now and forever, the border between Kyrgyzstan and Tajikistan will be the border of eternal friendship," Japarov said.

Japarov's office said the accord would contribute to "strengthening security, stability and sustainable development in Kyrgyzstan and Tajikistan, and in the whole of Central Asia".

The two leaders said direct air links would resume and the border, closed nearly four years ago in May 2021, would reopen.

The deal involves an exchange of territory.

Kyrgyzstan will receive about 25 square kilometres (nearly 10 square miles) from Tajikistan in exchange for about the same amount of land or for better access to shared water resources, Kyrgyz authorities said.

The accord stipulates that certain roads will be designated as neutral, and that neither side may hinder the use of agricultural or energy facilities in border regions.

Rakhmon hailed the "historic" agreement, which was concluded 33 years after the collapse of the Soviet Union.

Recent years have seen an improvement in relations between the five former Soviet republics in Central Asia -- Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan.

One by one, they have clinched border agreements designed to ease trade and enhance stability in the region, which is important for its resources and strategic location.

The Shanghai Cooperation Organization (SCO) -- which comprises China, most Central Asia coutries, Iran, India and Russia -- welcomed the Kyrgyz-Tajik treaty.

China, which has borders with both countries, has become a key player in Central Asia.

It is financing a colossal infrastructure scheme it calls the New Silk Roads, which aims to open up access to the mountainous region and facilitate trade with Europe.