A magnitude 6.4 earthquake has hit Central Asia's densely populated Ferghana valley, the US Geological Survey said.

Tuesday's quake, which struck 30km south-southeast Uzbek city of Ferghana in the east of the Central Asian country, measured 6.2 and was 9.2km deep, according to the US Geological Survey.

There was no immediate word on casualties or damage and it was not clear if the quake had hit a populated area.

Ferghana valley - split between Uzbekistan, Tajikistan and Kyrgyzstan in a confused patchwork of Soviet-era borders - is Central Asia's most densely populated area.

Tremors were felt across the vast mountainous region.

A resident of a Kyrgyz town near the Uzbek border, reached by Reuters by telephone, said the quake lasted up to 15 seconds. "It was very scary and long," said the Kyrgyz resident.

Earthquakes are frequent in Central Asia, a region of mountains and steppes set between Afghanistan, Iran, Russia and China.

In 2008, a powerful earthquake killed more than 70 people in Kyrgyzstan, a volatile country bordering Uzbekistan.

In 1966, the Uzbek capital Tashkent was flattened by a 7.5 earthquake when hundreds of thousands of people were left homeless. A 6 magnitude quake rocked Tashkent in 2008 but there was no damage.

Ferghana valley is a major centre of cotton and silk production, and the hills above are covered by walnut forests. The valley also has some oil and gas.

Source: Al Jazeera