Updated

A protest on Thursday over the influx of migrants in Greece ultimately turned violent.

Greek riot police fired tear gas at angry protesters on the island of Lesbos who had been trying to topple a police bus during a demonstration against a European Union migration policy.

“It has gone too far. Every day buses (with refugees) arrive, and they’re full,” protester Yannis Vaxevanis said. “The (government) has to do something and take the people somewhere else.”

The protesters were among 2,500 demonstrators who gathered in Lesbos’ main port as Prime Minister Alexis Tsipras arrived to speak at a conference. A large contingent of riot police formed a cordon to block the protesters from advancing, and scores of them then tried to push over a police bus in clashes that lasted more than an hour.

No arrests or injuries were reported.

Officers fired tear gas and earlier discharged several flash grenades.

A general strike Thursday virtually shut down the island to protest a 2016 agreement between the E.U. and Turkey that has left thousands of asylum-seekers stranded on Lesbos. Under the deal, migrants arriving on Greek islands from Turkey are held and face deportation to Turkey unless they successfully apply for asylum in Greece. The deal has created a massive backlog, angering people on Lesbos and other Greek islands.

Additional police officers, including antiriot units, were sent to Lesbos and took up positions around Mytilene. Supporters and opponents of the government used vans fitted with loudspeakers to promote the protest as well as a speech planned by the prime minister later Thursday.

More than 15,000 migrants and refugees remain stuck on Lesbos, Chios, and three other islands, most staying in severely overcrowded camps.

“Thousands of people are still living in appalling conditions with limited access to medical facilities,” the aid group Doctors Without Borders. Conditions at the largest refugee camp in Lesbos, the group said “were putting the health and lives of people stranded on the island at risk.”

Tension on the islands has been building as the number of migrants arriving from Turkey has risen sharply in recent weeks.

“The situation on the island is exceptionally difficult. We are feeling the effects of a long-term financial crisis and the way the refugee crisis has been handled,” Lesbos Mayor Spyros Galinos said. “For there to be any talk of growth or recovery, we must first be lifted out of this emergency situation.”

The government has promised to move thousands of asylum-seekers to the mainland but says the effort will take several months to implement — requiring additional staff and more shelter sites around Greece.

“Our aim is to deal with delays as swiftly as possible,” Tsipras said, before adding: “There are people who didn’t want me to visit the island and tried to scare (the government) away ... We did not run away.”

In the meantime, the number of daily arrivals continues to rise on the island and Greece’s land border with Turkey.

The Associated Press contributed to this report.