IDOMENI, Greece (AP) — 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 were removing hundreds of protesting migrants from a border crossing into 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 islet 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 enter the 28-nation European Union. More than 700,000 people have arrived so far this year. 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 further north.

Some Balkan countries, however, have stopped allowing anyone except those from war-torn countries to cross their borders, considering the rest not refugees but economic migrants seeking better jobs. Macedonia is allowing only people from Syria, Afghanistan and Iraq to cross, leaving thousands of others stranded on the Greek side of the border, where demonstrations have been frequent and sometimes violent

The protest 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.

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, nearly 30 buses carrying about 1,500 people headed south from the Idomeni border crossing area. The buses were expected later Wednesday in Athens, where authorities have set up shelters and will encourage the migrants to make asylum applications in Greece.

Police said 10 migrants were detained for resisting a transfer to the buses. Journalists and photographers were also briefly detained despite obeying police instructions to keep away from certain areas.

The freight rail line was expected to open later in the day.