Government officials have vowed to reduce severe overcrowding at migrant camps on Greek islands, amid mounting protests that the migrant crisis has hurt the vital local tourism industry for a fourth successive summer.

Migration Minister Dimitris Vitsas, visiting the island of Lesbos Wednesday, said the government aimed to reduce the number of migrants on five large Greek islands from the current level of 15,500 to 6,500 — equivalent to the capacity of refugee shelter facilities — by the end of September.

The changes were promised despite a recent spike in daily migrant arrivals at the islands and at Greece's land border with Turkey.

Prime Minister Alexis Tsipras is due to visit Lesbos Thursday, and islanders are planning street protests and a strike by businesses in the main port.