The hulking Greek coastguard officer gazed intently as another group of migrants, the fifth of the day, boarded a minibus after landing on a beach on the island of Lesbos.

“We’re taking it day by day,” he sighed, amid talk of a new refugee crisis, four years after nearly one million asylum seekers arrived on Europe’s doorstep, sparking EU-wide panic.

The UN refugee agency (UNHCR) announced on Tuesday that arrivals by sea from Turkey to Greece, mostly Afghan and Syrian families, increased to 10,258 in September.

It said this was the highest monthly total since 2016, when the EU reached an accord with Turkey to stem the flow of arrivals.

The surge has left an already overburdened Greek asylum camp network—which the UN terms “inhumane”—struggling to cope.

“In the last couple of months (there has been) an incredible contrast... a huge increase, quite sudden,” said Patrick Foley, emergency response coordinator for the Swedish NGO Lighthouse Relief that operates in the north of Lesbos, where most asylum seekers land.

“Each month is typically more than the month of the previous year”.

In May, the NGO was helping around 70 people land safely on Lesbos beaches and giving them temporary shelter.

This climbed to over 2,800 in September after similar numbers in August, Foley said.

“It’s really unpredictable. It could literally overnight just go back to normal again and it could be a short trend, or it could be a continued increase,” he said.

Greek islands opposite Turkey now host more than 26,000 asylum seekers in camps built to handle just a fraction of these numbers. In addition to poor hygiene and frequent outbreaks of violence, many of the residents sleep in tents and complain of having to queue for hours to obtain food, take a shower or use a toilet.