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MH17 shot down: Who did it?
02:12 - Source: CNN

Story highlights

Rebels have downed Ukrainian planes flying at high altitudes

A pro-Russian rebel commander shows off anti-aircraft missiles

The border region with Russia is very porous, unguarded in many places

Some contend that larger weapons have come into Ukraine from Russia

CNN  — 

Under a blazing sun in early June, a group of pro-Russian rebels in eastern Ukraine were digging amid pine woods near the town of Krazny Liman.

Their grizzled commander was a bearded man in his 50s who would not tell us where he was from, but acknowledged that he wasn’t local. He was proud to show off his unit’s most prized possession – a truck-mounted anti-aircraft unit that was Russian-made.

He told us the weapon had been seized from a Ukrainian base.

A few miles away, in the town of Kramatorsk, rebel fighters displayed two combat engineering tanks they said they had seized them from a local factory. Eastern Ukraine has long been a center of weapons production. They had parked one of the tanks next to the town square.

These were just two instances of how the rebels in eastern Ukraine were steadily adding more sophisticated weapons to their armory, including tanks, multiple rocket launchers – and anti-aircraft systems.

In early June, they began to target Ukrainian planes and helicopters, with some success.

The day after we met the commander in the pine woods, an Antonov AN-26 transport plane was brought down over nearby Slovyansk.

Several Mi-8 and Mi-24 helicopters were also hit in this period, as was an Ilyushin IL-76 cargo plane near Luhansk – it is about the size of a passenger jet.

Forty-nine military personnel were killed when the IL-76 crashed short of the airport.

For the most part, these aircraft were flying at relatively low altitudes, and were targeted by shoulde