A Greek defence ministry source said the migrants would stay on the transport ship until a new facility to accommodate them is created on the mainland.

Some 500 people, many of them families with small children, have been staying at the harbour since arriving from Turkey over the weekend.

In an effort to curb the influx, which erupted after Ankara said last week it would no longer stop refugees from entering Europe, Athens has suspended asylum procedures and bolstered its borders.

The new arrivals have exacerbated an already combustible situation on the Greek islands near Turkey.

Lesbos hosts more than 19,000 refugees and migrants crammed into squalid conditions around a camp built to house fewer than 3,000, a legacy of the 2015 migration crisis.

Fed up with shouldering the burden of Europe's over-stretched asylum system, locals have protested against the presence of the migrants on their shores, saying they threaten safety, public health and a tourism-dependent economy.

That anger has spilled over into violence in recent days, with an extremist minority accused of leading attacks on newly arrived migrants, intimidating media and targeting aid workers, according to several groups based on Lesbos.