MOSCOW, July 31 (RIA Novosti) - The head of the LUKoil Overseas Libyan office, who was detained in Tripoli last November, has been released and is back in Moscow, a source at the Russian embassy in Libya said on Thursday.

"[Alexander] Tsygankov has been released and is now in Moscow," the source said, adding that the official had arrived on the same flight as Libyan Prime Minister al-Baghdadi Ali al-Mahmudi, who begins an official visit to Russia on Thursday.

Dmitry Dolgov, a LUKoil official, has also confirmed Tsygankov's return to Moscow.

Although the Russian media said Tsygankov's arrest was connected to commercial espionage ahead of a December 9 tender for a dozen gas fields in Libya, no official charges were ever brought against him.

Russian gas monopoly Gazprom [RTS: GAZP] was eventually declared the winner of the December 9 tender.

Libya holds Africa's fourth largest gas reserves, estimated at 1.49 trillion cubic meters.

Tripoli first pledged to release Tsygankov during Russian Foreign Minister Sergei Lavrov's visit last December. Lavrov also repeatedly petitioned Libya to release Tsygankov in late January 2008.