One of the four Indians kidnapped in Sudan over three weeks ago was freed on Wednesday.

The release of Mohd Aseeb Shaikh early on Wednesday morning came after sustained efforts, including negotiations with the abductors, sources told PTI in Delhi.

Shaikh, who hails from Mumbai, was abducted alongwith three of his co-workers of a petroleum company on May 13 in the oil-rich Heglig area in southern Sudan.

The three others -- P K Abhilash from Kerala [Images], Biplab Biswas from Kolkata and Surjeet Singh from Amritsar [Images] -- continue to be in captivity.

They, too, are expected to be released soon, the sources said, citing information from Khartoum.

India's Ambassador to Sudan Deepak Vohra has been in close touch with the Sudanese authorities as part of efforts to secure the release of the hostages.

The four are employed with Petro Energy Contracting Services, an Indian-owned Sudanese company engaged in providing services to the Greater Nile Petroleum Operating Company of which ONGC [Get Quote] Videsh is a consortium partner.

The kidnapping was suspected to be the handiwork of some dissatisfied locals, who are unhappy at the benefits of oil resources not reaching them.

The Ministry of External Affairs had on May 21 summoned Sudanese Ambassador Abdel Rahman Mohammad Bekhiet to express concern over the kidnapping and press the African nation to secure their release urgently.