CHENNAI - India's top oil producer Oil and Natural Gas Corp Ltd said three of its employees were kidnapped by gunmen from a rig site in the eastern Assam state on Wednesday.

The employees were kidnapped in a company-owned vehicle from the state-run firm's Lakwa field in Assam's Sivasagar District, where the exploration company has been operating for nearly six decades.

"The vehicle was found abandoned near the Nimonagarh jungles close to the Assam-Nagaland border," ONGC said in a tweet.

Assam is among the top three oil producing states in the country, and production delays due to safety issues could hamper India's efforts to reduce oil imports by 10% by 2022.

ONGC did not comment on whether oil production would be impacted by the incident, but said it had filed a complaint with local officials.

Local police said they suspected the United Liberation Front of Asom-Independent (ULFA-I), an armed separatist group in the region, to have carried out the abduction.

"Based on the region and the way this incident happened, we suspect the ULFA-I could have carried out the abduction," Amitava Sinha, the top police officer in the district told Reuters.

Two employees of Quippo Oil and Gas Infrastructure Ltd, a private exploration firm, were kidnapped in December in Arunachal Pradesh state, located on India's far east, according to local media reports.

Two ONGC engineers were infamously shot dead in Assam by ULFA-I in the early 90s, and an engineer from Oil India Ltd, another state-run firm, was abducted in 2006.

"Higher officials of the State Police are on the site," ONGC said, adding that it was "in constant touch with the higher authorities."

Indian markets were closed on Wednesday. ONGC had closed marginally lower at 102.85 Indian rupees on Tuesday.

(Reporting by Sudarshan Varadhan; Editing by Jacqueline Wong and Christopher Cushing) ((Sudarshan.Varadhan@thomsonreuters.com; +919810393152; Twitter: https://twitter.com/sudvaradhan @sudvaradhan;))