Greek police on Thursday completed the evacuation of the sprawling border camp of Idomeni by removing nearly 800 migrants, a police source said.

"We're done. No more people remain, just tents with supplies belonging to aid groups," the officer told AFP.

In the space of three days, police transferred about 4,000 migrants by bus from Idomeni to newly-created camps in the industrial outskirts of Greece's second city Thessaloniki.

But most of the 8,400 people at the camp when the operation began on Tuesday refused to join the operation, the officer said.

"Most of them have gone outside gas stations and hotels nearby, or have walked to camps on their own," the officer said.

Idomeni camp had become a potent symbol of human suffering and chaos as Europe struggles with its worst migrant crisis since World War II.

The camp reached over 12,000 people, who spent a brutal winter in freezing rain and mud after Macedonia and other Balkan states closed their borders in mid-February to stem the influx to northern Europe.

Many tried to force their way across the border, sometimes resulting in violent encounters with Macedonian police.