A wooden smuggling boat carrying about 50 people sank Wednesday in the eastern Aegean Sea. Greek authorities said at least 12 people drowned, including six children, and 12 others were missing.

In northern Greece, riot police removed more than 2,000 migrants who had been protesting for weeks at a border crossing with Macedonia, which is denying them entry.

Greek coast guard and navy vessels, a helicopter and a vessel from the European border agency Frontex were searching for survivors off the Greek island of Farmakonissi after the boat sank early Wednesday. Authorities said 26 people were rescued.

Weather conditions in the area were good but survivors told the coast guard the boat had begun taking on water shortly after setting sail from Turkey.

Greece is the main entry point for asylum-seekers trying to get into the 28-nation European Union, and about 770,000 people have arrived so far this year. More than 200 have drowned so far, and at least 120 more are listed as missing.

Few want to remain in financially stricken Greece, with almost all heading to the border with Macedonia then through the Balkans to more prosperous European nations.

Some Balkan countries, however, have stopped allowing anyone except those from war-torn countries to cross their borders, considering the rest not refugees in danger but economic migrants who just want better jobs. Macedonia is allowing only people from Syria, Afghanistan and Iraq to cross in, leaving thousands of others stranded on the Greek side of the border.

Migrants have protested the new restrictions and sometimes the demonstrations at the Idomeni border crossing have turned violent. The unrest has severed a key Greek freight train link with northern Europe for three weeks and also periodically prevented refugees that Macedonia will accept from crossing the border.

About 350 Greek police launched an operation just after dawn Wednesday to clear the migrants — many of them from Iran, Morocco and Pakistan — from the border area.

Escorted by police motorcyclists and patrol cars, 45 buses carrying about 2,300 people headed south from Idomeni to Athens, where authorities set up shelters and will encourage the migrants to make asylum applications in Greece.

A member of the Doctors of the World charity at the border said there were few tensions Wednesday between police and migrants.

"Things were generally calm, because the migrants didn't react," surgeon Vassilis Naoum said. "In some cases where they did, I saw them being detained ... this happened to at least 30 people."

Police said 10 migrants were detained for resisting a transfer to the buses. It was not possible to immediately reconcile the different numbers of detentions.

Journalists and photographers were also briefly detained despite obeying police instructions to keep away from certain areas.

The freight rail line opened later in the day, with two trains crossing into Greece from Macedonia.

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