The number of Russian civilians traveling to Syria, where Moscow is running a military operation in support of President Bashar al-Assad, reached record levels this year, according to official figures published by a Russian security service.
The data does not include Russian servicemen or explain what the civilians are doing in Syria.
But the figures shed some light on the scale of Russian activities in Syria because they appear to include civilian personnel working for the military and may also reflect the presence of private military contractors who, according to people familiar with the deployment, are fighting in Syria in support of regular Russian troops.
The number of Russian civilian trips to Syria grew after President Vladimir Putin announced a partial withdrawal of troops last December, an increase apparently indicating an expansion of Moscow's activities in the country.
The numbers of departing Russian citizens are counted by destination countries and are published every quarter by the Federal Security Service (FSB), which supervises border guards, on a government statistical website.
In the first half of this year the FSB registered more than 17,000 departures by Russians to Syria, more than in any six-month period since the Russian operation began in September 2015.
There were nearly 22,000 departures in the whole of 2016 and more than 25,000 in 2017. The number of Russians traveling to Syria may be less because some may make several trips. The FSB has published no data on Russians returning from the country.
Late last year, Putin flew to Syria to announce mission accomplished and to order the withdrawal of "a significant part" of Moscow's military contingent. Russia does not disclose how many troops it has in Syria.
In August, Russian Defence Minister Sergei Shoigu said more than 63,000 Russian servicemen had earned combat experience in Syria since 2015, but troop rotation means the size of the deployment remains unclear.
The number of civilian trips from Russia to Syria has risen more than 10 times since Russia started preparations for its Syria operation in mid-2015. Putin announced the Russian deployment on Sept. 30 of that year.
Only about 1,800 Russians travelled to Syria in each of 2013 and 2014. The first half of 2015 was no different, but the number of departures grew five times just before the official start of the operation and doubled again after it began.
The number of Russian tourists going to Syria has hardly changed in the last five years, numbering just dozens per year.
The Kremlin, the Defence Ministry and the Foreign Ministry had no immediate comment.
The data on Russia civilian trips to Syria is publicly available but has not been previously reported.
Thousands of Russian private military contractors travel privately to Syria, multiple sources familiar with the deployment have told Reuters. They have civilian status although they cooperate with the military command.
Russian officials deny involvement in the contractors's activities, saying volunteers from Russia can fight in Syria on their own.
Departures to Syria are categorized according to the purpose of visits. Most Russian civilians go on "working trips", "private trips" or as "transport support personnel".
The headings do not refer to private military contractors. However, friends and relations say the contractors are civilian sand Reuters reporters have observed groups of them traveling to Syria from a civilian airport in Russia that has international departure and passport control procedures.
The Russian army makes wide use of civilian personnel, and commanders of military units, as well as other senior military officials, can employ them, according to an order published on the Defence Ministry website.
The number of trips made by transport support personnel reached its highest level – 1,678 departures in three months – in the first quarter of this year.
Most people listed travel by air, although the numbers traveling by sea are rising.
Russian civilians made 868 trips by sea in the first half of this year, compared to 1,053 trips during the whole of last year and 59 in 2016.
The FSB data is unlikely to include Russians going to Syria to fight against the government because, as several fighters have told Reuters, they enter Syria illegally from Turkey. The data only captures direct travel between Russia and Syria.