SLOVIANSK, Ukraine/MOSCOW (Reuters) - On Feb. 12 last year, the same day that a ceasefire ended the worst of the fighting in eastern Ukraine between rebels and government forces, a former rebel fighter seized a chance to turn his inside knowledge of the conflict into hard cash.

A Ukrainian serviceman checks documents at a checkpoint near Slaviansk in Donetsk region, Ukraine, June 29, 2016. Picture taken June 29, 2016. REUTERS/Gleb Garanich

He traveled to a spot on the Russian-Ukrainian border where he retrieved a cache of weapons hidden there earlier by his comrades in the pro-Russian rebel movement.

Four days later, shortly before 6:00 p.m., he and a friend showed up in a taxi at a fuel station in western Russia where they had arranged to meet a contact ready to buy the arms, according to Russian court documents.

MORE FROM REUTERS:

Cold War ghosts haunt Latvia amid renewed NATO-Russia tensions

Afghan teenager met Munich gunman just before attack: prosecutor

U.S. praises confidence-building measures with Chinese military

He and the friend opened the trunk of the taxi, and began transferring the cargo into the buyer’s vehicle. Concealed in a sports bag and a rucksack were three automatic weapons, 1,258 bullets, 20 grenades, and 20 detonators for the grenades.

The buyer was an undercover police officer and the former rebel, identified in the court documents as Y.V. Mikhailov, was sentenced this year to two and a half years in jail.

The fighting in eastern Ukraine between the Moscow-backed separatists and Ukraine’s pro-Western government killed hundreds of people, displaced thousands of residents and created a Cold War-style stand off between Moscow in the West.

It also had another consequence that is less visible but could in time prove equally dangerous: the conflict took huge amounts of arms out of government arsenals and put them in the hands of irregular units unable to properly control them.

Now the fighting has subsided, according to security officials and experts on the arms trade, the weapons are getting into the hands of criminals and being spirited to buyers well beyond the conflict zone.

Interviews by Reuters with security officials and rebels, as well as study of law enforcement data and court documents have shown that weapons are being channeled out of the conflict zone in eastern Ukraine in significant numbers, in some cases as part of an organized underground trade.

“Of course, they have moved arms across, and they’re moving them across now,” Igor, a fighter with a pro-Russian rebel unit in eastern Ukraine told Reuters in an interview. “Mainly they take Kalashnikovs,” he said.

ARSENALS PILLAGED

When, in the spring of 2014, the armed rebellion started in Ukraine’s Russian-speaking regions of Donetsk and Luhansk, police and soldiers abandoned their bases.

That left the rebel militias to pillage the stores where Ukraine -- one of the world’s biggest arms manufacturers - kept its sizable arsenal.

Slideshow ( 4 images )

Meanwhile on the pro-Ukrainian side, because the army was in near-collapse, irregular militias were formed, some of them only loosely part of the chain of command, and they were given, or scavenged, weapons from official supplies.

While the fighting raged, the weapons stayed in the conflict zone. In February 2015, the sides in the conflict agreed a ceasefire. The fighting did not stop, but the intensity subsided, and weapons started leaking out of the battlefield.

Official data is patchy but what figures there are indicate the problem is getting worse. The number of prosecutions for weapons offences so far this year in Ukraine is double the amount for the whole of 2015, according to the general prosecutor’s office.

In many cases, the cause is negligence. Irregular units often do not keep proper control of the weapons in their inventories or fail to make soldiers surrender their guns when they go on leave.

“It’s mostly people taking them home for the sake of it,” said Serhiy Alyoshin, the chief of police in the town of Sloviansk, which is on the edge of the conflict zone and controlled by Kiev.

“Some say ‘I forgot’, some say ‘It’s for fishing’ or ‘It’s a present for a friend’ and then we hear about these things blowing up in apartments, in yards and on the street. It’s a threat to national security.”

In some cases, Ukrainian security officials said, irregular pro-government units set up private weapons caches to avoid surrendering their arms to the authorities in Kiev, whom they do not trust.

In March this year, the police force in Sloviansk uncovered a cache of weapons and explosives in the back of a garage filled with cardboard boxes and household junk.

In police footage seen by Reuters, officers laid the weapons and explosives out on the ground. There were at least three anti-tank rocket launchers, several rockets, hundreds of bullets, around 15 hand grenades and two anti-tank mines.

ORGANIZED CRIME

But there is evidence too of criminal intent to smuggle weapons out for sale to organized crime groups.

“Of course, anyone who has the will and the means can get into the business - organized criminal groups have always traded weapons,” said Olena Hitlyanska, a spokeswoman for Ukraine’s State Security service, or SBU. “Now the channel for buying these illegal weapons has widened,” she said.

“In past years we seized pistols and rifles that people had in their own collections or for hunting. Now grenade launchers are seized, and blocks of TNT.”

Igor, the rebel fighter, said there was now a well-organized trade in illegal weapons from eastern Ukraine into Russia.

“If before they shipped whatever came to hand, now it happens in a more orderly fashion, practically by appointment,” said Igor, who asked to be identified only by his first name for fear of reprisals for speaking about the trade.

In one rebel unit “they practically keep a list of who will take the iron across the border and when,” he said, using a slang term for weapons.

He said the weapons were smuggled from rebel-controlled eastern Ukraine into Russia via illegal border crossings.

He said much of the smuggling was done by rebel fighters from Chechnya and Ingushetia, in Russia’s volatile North Caucasus region, who ship the weapons back home.

A spokesman for the rebel administration in eastern Ukraine’s Donetsk region, Eduard Basurin, said about arms smuggling: “Maybe at one point it was present, but that this is being done in an orchestrated way, that’s rubbish.”

DESTINATION: MIDDLE EAST

So far, there is little evidence of where the weapons smuggled out of the Ukraine conflict zone end up.

In May, Ukrainian border guards detained a 25-year-old Frenchman with ties to far-right groups in France who was trying to cross from Ukraine into Poland with weapons including rocket launchers and Kalashnikov assault rifles in his Renault van.

Ukraine’s SBU said the man had made contact with armed militias in Ukraine and inquired about buying arms from them. When they found out about this, the SBU said its agents sold the man deactivated weapons.

But that case appears to be an outlier. The illegal arms trade in western Europe -- where the items most in demand are small quantities of light firearms -- is dominated by supplies from ex-Yugoslavia, and it is unlikely Ukrainian weapons would be able to break into that market.

Instead, most of the weapons from Ukraine will be destined for other conflict zones in places such as Iraq, Syria and Libya where there is a demand for heavy weapons in large enough quantities to make it worthwhile for black market arms dealers.

Mark Galeotti, an expert on ex-Soviet organized crime, said some of those Ukrainian weapons would be transported through the Ukrainian Black Sea port of Odessa, then into the Mediterranean, some south through the Balkans, and some through Russia’s North Caucasus region.

“Usually it is relatively easy to get a pistol or anything up to an assault rifle,” said Galeotti, senior research fellow at the Institute of International Relations Prague.

“But it is much harder to get an RPG (rocket-propelled grenade) or a machine gun or the boring things like spare parts for the above. You actually need to have a proper war for these sorts of things to become available and, lo and behold, you have a proper war,” he said.

“At the moment you have, from the criminals’ point of view, a wonderful opportunity.”