MOSCOW (Reuters) - Groups representing Russian military veterans plan to ask the International Criminal Court (ICC) to investigate Russia’s secret deployment of civilian contractors in Syria, Ukraine and Africa, a paramilitary leader said on Friday.

The recruitment of civilians to fight abroad is illegal in Russia, and the Kremlin has repeatedly denied reports of thousands of Russian private contractors fighting alongside government forces in Syria. Over 100 Russian civilians were killed during the campaign, according to people familiar with the mission.

However, the ICC has no jurisdiction over Syria and has never handled any cases like this before.

More than a dozen Russian veteran organizations plan to write to Fatou Bensouda, prosecutor of the Hague-based ICC investigating war crimes, according to Yevgeny Shabayev, a paramilitary Cossack group leader who says he personally knows dozens of people who have been on such assignments.

It is unclear how big the organisations on the list are and they may not represent a significant majority of veterans - of whom there are hundreds of thousands in Russia following its intervention in Afghanistan and the conflict in Chechnya.

A letter of appeal from the groups will urge Bensouda to initiate a probe into recruitment of the Russian mercenaries.

“The Russians fight abroad as “volunteers” and without an official recognition from the Russian government,” said Shabayev, who has once served as a representative of one of self-proclaimed pro-Russian separatist republics in eastern Ukraine.

The veterans, some of whom are close to the mercenaries, say in the letter they are unhappy with the fact that private contractors operate illegally and enjoy no social benefits or protection afterwards.

“In fact Russian civilians ... are being sent out of their country of residence to be illegally used for military purposes.”

The Kremlin and the Russian Defence Ministry did not reply immediately reply to requests for comments. A spokeswoman for Bensouda’s office said by email she was unable to comment.

Several hundreds delegates plan to discuss the document at a forum on Nov. 18 in Moscow and mail it to the ICC the next day, Shabayev said adding that they have worked on the document for several months.

Russian citizens were seen in large numbers taking part in the fighting in eastern Ukraine on the side of pro-Russian separatists. Moscow said they went there on their own will as volunteers.

The Kremlin officially deployed 170 civilian instructors in the Central African Republic and plans to send 60 more to reinforce them - a mission which Moscow says has been approved by the U.N. Security Council.

Last year, a Russian private security company said it carried out a demining mission in Libya.

The veteran organizations said in the letter of appeal that Russian contractors also worked in Sudan, South Sudan, Yemen and Gabon.

The authors said in the document they would assist the ICC if it launched an investigation. Shabayev said some former Russian private military contractors who had fought abroad would be ready to testify if the offered them protection.

“It will depend on whether the West is really interested in examining the situation,” Shabayev said.

It was not immediately clear whether or how the ICC would respond to the group’s message.

The ICC has jurisdiction only when a country’s own government is unwilling or unable to prosecute an extremely grave crime, and only over crimes committed on the territory of its member states. Russia is not a member.