Greece appealed to its European Union partners on Tuesday to come up with a comprehensive strategy to deal with a growing migrant crisis as new data showed 21,000 refugees landed on Greek shores last week alone.

That number is almost half Greece’s overall refugee intake in 2014 and brings total arrivals this year to 160,000, even as it struggles with a debt crisis that has forced it to accept a third international bailout.

The influx of refugees, mainly from Syria, has strained an already ill-prepared reception system in Greece that relies heavily on volunteers, forcing thousands to camp out in filthy conditions and triggering sporadic clashes and brawls.

A spokesman for the United Nations refugee agency UNHCR in Geneva said Greece needed to show “much more leadership” in dealing with the crisis.

But Greek officials said they needed better coordination within the European Union. “This problem cannot be solved by imposing stringent legal processes in Greece, and, certainly, not by overturning the boats,” said government spokeswoman Olga Gerovassili.

Nor could it be addressed by building fences, she said.

Earlier this month construction began on a 175 km (110 mile) razor wire border fence in Hungary to deter migrants, while Britain and France have tightened security on the French side of the 30-km (19-mile) tunnel linking the countries.

Greece, which is in the throes of its worst economic crisis in generations, criticised other European countries for being more of a hindrance than a help as bottlenecks were reported not only in getting into the country, but getting out on its northern land borders.

“This country doesn’t have the financial resources or the infrastructure to get through this in a dignified manner,” Gerovassili said.

In addition to overcrowded conditions on some of its Aegean islands, problems were compounded by a lack of transport to take refugees to the Greek mainland at the peak of the summer vacation season.

“There are about 4,000 people waiting for transfer on Lesbos right now and arrivals are continuing,” said Katerina Selacha, a volunteer with Aggalia, a non-governmental organisation on the Greek island. “Conditions are pretty difficult.”

International Rescue Committee said Lesbos risked “reaching breaking point” due to the spike in the number of arrivals over the past few days and the inability for refugees to leave.

“The situation is already volatile and we have started seeing increased tensions with the local authorities and between different refugee groups,” said Kirk Day, the aid agency’s emergency field director on the island.

UNHCR officials said only three Greek islands had organised reception facilities for refugees but that they were inadequate.

There were chaotic scenes on the island of Kos last week, where local police locked migrants in an outdoors athletics stadium to process them. On one occasion police used fire extinguishers to keep crowds back.

The Greek state eventually charted a passenger ship to house and process migrants in an attempt to ease conditions onshore, where many are living in tents, some in shelters made from cardboard boxes.

Gerovassili said more reception centres were required.

“We must have new reception facilities … We cannot continue to see these tragic images of children, people living under such circumstances.”