THESSALONIKI, Greece — Migrants and refugees around Greece staged demonstrations at four sites Thursday to protest delays in implementing asylum procedures promised under a European Union agreement with Turkey.

Around 500 migrants chanting “open the borders” gathered in Thessaloniki.

“I’ve been here for six months and we are still trapped here. People reaching Italy can cross borders. But we are not allowed to, I don’t understand why,” said Abdo Rjab, a 21-year-old Syrian.

Protests were also held Thursday on the islands of Chios and Lesbos, while scores of migrants at a camp near the Greek-Macedonian border in the north of the country blocked the main highway linking the two countries for about 30 minutes.

Police announced no arrests at any of the protests.

Some 60,000 migrants remain stranded on Greece’s mainland and the islands.