Uzbek President Islam Karimov, 78, has died after suffering a stroke, according to diplomatic sources.
Although the Uzbek government has not yet confirmed the news, a senior diplomat was quoted saying "Yes, he has died" while speaking to Reuters.
Binali Yildirim, Prime Minister of Turkey, was the first foreign leader to offer condolences over the death of Karimov.
Karimov, who ruled Uzbekistan since 1989, first as the head of the local Communist Party and then as president of the newly independent republic from 1991, has not left any obvious successor to take over the central Asian nation of 32 million people.
The transition of power is likely to be worked out by a small group of senior officials and family members. However, many fear that if a compromise is not worked out, Uzbekistan, which shares a border with Afghanistan and has become a target for Islamist militants, may destabilise.
Among potential successors to Karimov are Prime Minister Shavkat Mirziyoyev and his deputy Rustam Azimov. Security service chief Rustam Inoyatov and Karimov's younger daughter Lola Karimova-Tillyaeva may become kingmakers.
According to the country's constitution, the chairman of the upper house of parliament is supposed to take over after Karimov's death, and elections must take place within three months.
However, analysts don't consider Nigmatilla Yuldoshev, the chairman of the upper house of parliament, as a serious contender.
Karimov's successor will be tasked to resolve tensions with ex-Soviet neighbours Kyrgyzstan and Tajikistan over border issues and the use of common resources such as water.
