Though he's been released, it's unclear which group was behind the kidnapping of a member of the Libyan National Oil Co., his family said.

Samir Kamal, a member of the NOC's planning committee, disappeared Jan. 15 while leaving his office in Tripoli. He was released Sunday, though no group has yet to claim responsibility for his kidnapping.

"He is well, but of course shaken up," a family member told the Libya Herald. "The reasons for his kidnapping are unclear, and the people responsible are still unknown."

Kamal has represented Libya's interests at the Organization of Petroleum Exporting Countries as the country struggles to resume its North American dominance in the 12-member group. OPEC in its January market report said continued unrest in Libya led to "significant disruption" in oil production from the country.

Libyan oil production in December, the last full month for which data are available from OPEC, was around 489,000 barrels per day, down more than 25 percent from the previous month. Libyan oil production before NATO-led intervention in its 2011 civil war was more than 1 million bpd.

Recent internal skirmishes have split Libya between the Islamist government in Tripoli and the United Nations-recognized government in the east of the country.