Man-made hazards threaten migrants crossing Mediterranean Sea

At least 34 migrants drowned when their crowded boat capsized in high winds off Greece. Fifteen were children.

The risky journey, across the Mediterranean Sea to Europe, has claimed more than 2,500 lives so far this year. But refugees are also being harassed at sea -- further endangering their lives.

An inflatable raft was intercepted just a few miles off shore by the Turkish coast guard.

They tried to force it back -- firing a warning shot over the heads of those on board. And then two more shots -- terrifying the men, women and children in the raft.

As they crossed into Greek territorial waters, the Turkish coast guard finally moved away.

It follows CBS News' investigation last week. We filmed men on an unmarked speed boat approaching from Greek waters.

A refugee filming on board hid his camera but told CBS News the men were dressed in black and pointed guns at them. Then, they cut the fuel supply to their motors, leaving the refugees adrift on the open sea -- and frightened for their lives.

Those attempting the perilous crossing to Europe must now also risk harassment and sabotage.

The Greek coast guard told CBS News Monday that it has now launched an investigation into the incident that we witnessed - which it says was reprehensible. But the Greek coast guard has not said whether its men were involved.