MOSCOW, April 11 (Xinhuanet) -- A Dutch medical aid worker abducted 20 months ago in southern Russia was freed Sunday in a rescue operation, Russian officials said, but many questions concerning the kidnapping remain unclear.

    Arjan Erkel, 35, head of the medical charity Medecins Sans Frontieres (MSF), was abducted in Dagestan near the restive republic of Chechnya on August 12, 2002 by unidentified assailants.

    Dagestani Interior Ministry's spokesman Abdulmanap Musayev said Erkel was freed in a pre-dawn special operation Sunday jointly performed by the ministry and local FSB intelligence agency, the Interfax news agency reported.

    MSF spokesman in Russia Mark Walsh did not comment on whether Erkel was freed in a rescue mission, but he said no ransom had been paid.

    The MSF official said Erkel has arrived in Moscow and is on the premises of the Dutch embassy here.

    Erkel looks very tired but can walk, and will undergo a thorough medical examination soon, according to Walsh. He said earlier that there is no need for Erkel to return to the Netherlands for medical assistance.

    The identity of the kidnappers and Erkel's whereabouts over the past 20 months have been unknown, but the release itself is a major development, Interfax cited humanist Anna Neistat as saying.

    Neistat, head of the Human Rights Watch's Moscow branch, pointed out that the case should not be brought to an end until all the questions are answered.

    The MSF has repeatedly accused the role of Russian authorities in the kidnapping. A senior MSF official has blamed the inconsistent investigation into the case, claiming that Russian officials managed to establish close contact with the abductors.

    However, Moscow has denied all MSF allegations.

    Dagestan is the eastern neighbor to the war-torn Chechnya, where conflicts between Russian troops and separatists claim dailylives on both sides and kidnappings of civilians are constantly reporded.

    International aid groups have drastically reduced their presence and MSF suspended its operations in the region after Erkel's abduction. Enditem