IDOMENI, Greece (Reuters) – More than 1,000 migrants streamed out of a camp near the northern Greek border on Monday to try to find a way around a border fence blocking their way into Macedonia, Reuters witnesses said.

A large group of migrants marched away from the sprawling tent city near Idomeni, where at least 12,000 people have been stranded in filthy conditions since Macedonia and other nations blocked their route north along the so-called Western Balkan route, a Reuters TV crew said.

Later a second group of 500 migrants set off from Idomeni to follow them.

(DANIEL MIHAILESCU/AFP/Getty Images)

They were trying to find a gap in the barbed wire fence that Macedonia has built along its border to deter the migrants, many of whom come from war zones in Syria and Iraq. They want to head north to wealthier European Union nations such as Germany.

Heading west from the camp in a long snaking cavalcade along muddy paths, the migrants, wrapped up in coats and hats, carried their belongings in rucksacks and bags. The group included many children, some walking, others pushed in strollers.

Some of the migrants made victory signs as they walked along. There was no sign of police following the migrants.

When they reached a river, the migrants passed a rope across it and formed a “human chain” to cross, Reuters photographer Stojan Nenov said. Migrants carried children across on their shoulders.

Migrants cross a river as they try to walk to the Macedonian border after deciding to leave the Idomeni refugee camp on March 14, 2016 in Idomeni, Greece. (Matt Cardy/Getty Images)

After crossing the river, the migrants reached the border fence and walked along it trying to find a way through into Macedonia.

Earlier, Macedonian police said three migrants – two men and a woman – had drowned while trying to cross a river close to the Greek border that had been swollen by heavy rain.

(DANIEL MIHAILESCU/AFP/Getty Images)

Greece has stepped up efforts to move thousands of migrants near the Macedonian border to sheltered camps amid fears about the spread of infectious diseases.

EU leaders and Turkey are due to meet again on Thursday and Friday to seal a deal to try to stem illegal migrant flows from Turkey to Europe through Greece.

(Reporting by Branko Filipovic; editing by Adrian Croft and Gareth Jones)