Gunmen have kidnapped dozens of Tunisians in northwestern Libya to demand the release of a local Libyan official arrested in Tunisia this week, families and locals sources said on Tuesday.

An official from Sabratha, a coastal town between Libya’s capital Tripoli and the Tunisian border, was arrested along with another Libyan at Tunis airport on Saturday, Sabratha’s municipal council said.

They had flown to Tunis on a visit organized by United Nations, the council said. Tunisian officials were not immediately available to comment.

“Gunmen kidnapped my father… We talked with the kidnappers over the phone and told us they would release them only when Tunisia frees the Libyan officials arrested in Tunisia,” the daughter of one of the detained Tunisians told local radio. “I ask the authorities to intervene.”

Mustapha Abd El Kebir, a Tunisian human rights activist with contacts in Libya, said dozens of Tunisians were being held in Sabratha.

Armed groups in chaotic Libya often act with impunity because of a security vacuum in which two rival governments and their armed backers fight for control of the North African state four years after Muammar Gaddafi’s fall from power.

Tunisians and other foreign nationals have been kidnapped or detained in the past to pressure their governments to release Libyans held overseas.

An armed group stormed the Tunisian consulate in Tripoli and kidnapped 10 staff this year before releasing them. Tunisia closed the consulate after the kidnapping.

Relations between the North African neighbors have become increasingly tense, with Tunisia’s government worried about spillover from the chaos that continues to plague Libya after the 2011 revolt against strongman Qaddafi.

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