Kazakh President Nursultan Nazarbaev says he and his Russian counterpart, Vladimir Putin, are very concerned with the situation in Tajikistan.
Nazarbaev was speaking at a joint press conference with Putin after talks in the Kazakh capital, Astana, on October 15.
Tajikistan shares a border with Afghanistan, where the Taliban has stepped up attacks in recent weeks.
Tajikistan itself witnessed a deadly alleged mutiny by a serving deputy defense minister in September.
Nazarbaev also said "Kazakhstan has been, continues to be, and will remain the closest and most reliable neighbor and ally of Russia."
Nazarbaev praised the Eurasian Economic Union, a Moscow-led grouping bringing together Armenia, Belarus, Kyrgyzstan, as well as Russia and Kazakhstan.
Nazarbaev said “a great number of countries” were eager to work with the bloc.
For his part, Putin said bilateral ties with Kazakhstan were "a true allied relationship in every sense of the word."
Putin said the two countries have "big plans" to drill for oil in the Caspian Sea.