Police have clashed with some 300 migrants and refugees at the Greek border with Macedonia, as protests intensified and thousands ignored government instructions to move to organized shelters.

Youths threw rocks at riot police who withdrew from the area without making any arrests, authorities said Tuesday.

The protesters have blocked freight rail tracks for the past eight days, demanding that the border reopen. Macedonia says the border will remain closed to all migrants at least until the end of the year.

Some 12,000 people remain camped out in harsh conditions near the border village of Idomeni, despite daily calls by the government to move to nearby shelters built by the army.