Macedonia toughened rules for crossings earlier this month, in the wake of the deadly Paris attacks, restricting access to citizens from countries typically granted asylum in Europe, including Syria and Afghanistan.
At least 10 people stranded at the border are on hunger strike and have sewn their mouths shut in protest. One of the hunger strikers fainted during the protest and was carried by to a medical tent set up by a charity organization.
An Iranian migrant who asked to be identified only by her first name, Sonya, said she was afraid to return to Iran after speaking out against authorities there.
"They are not letting us into Macedonia. I have tried to cross at several points, but the police were always there to stop us," she said.
"I`ve been here for seven days and I`m going to keep trying to get across."
About 750 stranded migrants remained camped out near the border village of Idomeni, police said. They have staged daily demonstrations at the border, and have pitched their tents on a railway line, halting rail services between the Greek port of Thessaloniki and the Macedonian capital Skopje.
With many of its islands facing the coast of Turkey, Greece was the busiest entry point for migrants and refugees trying to reach northern Europe following a spike in new arrivals this year.
Struggling to cope with the high numbers of new arrivals, many Balkan countries relaxed transit rules over the summer as migrants headed to Germany and other countries northern Europe.
Greek police said 2,400 migrants had crossed into Macedonia in the 24 hours before 6 a.m. (0400GMT) Thursday, down from the recent daily average of 3,500.
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