Turkmenistan (or ; Turkmen: Türkmenistan, pronounced [tʏɾkmønʏˈθːɑːn]), also known as Turkmenia, officially the Republic of Turkmenistan, is a country in Central Asia, bordered by Kazakhstan to the northwest, Uzbekistan to the north, east and northeast, Afghanistan to the southeast, Iran to the south and southwest and the Caspian Sea to the west. Ashgabat is the capital and largest city of the country. The population of the country is about 6 million, the lowest of the Central Asian republics. Turkmenistan is one of the most sparsely populated nations in Asia. Citizens of Turkmenistan are known as Turkmenistanis, Turkmenians or Turkmens.Turkmenistan has been at the crossroads of civilizations for centuries; Merv is one of the oldest oasis-cities in Central Asia and was once the biggest city in the world. In medieval times, Merv was also one of the great cities of the Islamic world and an important stop on the Silk Road. Annexed by the Russian Empire in 1881, Turkmenistan later figured prominently in the anti-Bolshevik movement in Central Asia. In 1925, Turkmenistan became a constituent republic of the Soviet Union, the Turkmen Soviet Socialist Republic (Turkmen SSR); it became independent after the dissolution of the Soviet Union in 1991.Turkmenistan possesses the world's fourth largest reserves of natural gas. Most of the country is covered by the Karakum or Black Sand Desert. From 1993 to 2017, citizens received government-provided electricity, water and natural gas free of charge.The sovereign state of Turkmenistan was ruled by President for Life Saparmurat Niyazov (also known as Türkmenbaşy or "Head of the Turkmens") until his death in 2006. Gurbanguly Berdimuhamedow was elected president in 2007 (he had been vice-president and then acting president previously). Turkmenistan has been widely criticized for its poor human rights. Notable issues were its treatment of minorities, press freedoms, and religious freedoms. After the suspension of the death penalty, the use of capital punishment was formally abolished in the 2008 constitution.