The authorities detained at least 700 people who crossed the border by fording a swollen stream near the Greek village of Hamilo, police in the former Yugoslav Republic of Macedonia said on Tuesday. At least 50 journalists and volunteers were also detained and fined 250 euro ($280) for illegal border crossing, according to a Macedonian official.

The group had been taken back through their point of entry, some 5 kilometers (3 miles) from the Greek border camp of Idomeni.

A second group of about 600 migrants was prevented from crossing and spent the night in the Greek mountains, according to a Reuters photographer. Also, a number of migrants are reportedly still in Macedonian territory.

Refugees have been attempting to continue their journey toward northern Europe by going around the fence which blocks entry from Idomeni into Macedonia.

Rumors in the camp

Greek Prime Minister Alexis Tsipras blamed the mass push on leaflets distributed in the crowded Idomeni camp.

According to Tsipras, "unknown people, perhaps groups that call themselves volunteers," handed out leaflets advising migrants to head north and warning them against traveling to government-provided shelters in Greece. The flyers described the route across the river in Greek and Arabic.

"This is criminal behavior toward people who face great hardship," Tsipras said. "This must stop."

Macedonian media reported that at least three Afghans had drowned while attempting to cross.

The refugees in Idomeni have grown frustrated by deteriorating conditions in the camp, where many migrants are forced to sleep outside despite days of rain. The camp currently holds some 12,000 people, even though it was set up for no more than 2,000.

'No chance' for Balkan route

UNHCR spokesman Babar Baloch said that the migrants' breakout and return "hasn't solved anything."

"It just increased sufferings of refugees. It started raining again. The sense of support for refugees in the region is missing," he said from the scene in Idomeni.

The EU leaders are due to hold a joint summit with Turkey later this week to finalize a deal on stemming the flow of refugees. Meanwhile, thousands of people remain stuck at border crossings after countries along the so-called Balkan route closed their doors.

On Tuesday, Tsipras said there was "no chance" for borders to open and urged migrants to move to shelters.

"We therefore urge them to move to reception centers the Greek government has created for them, in humane conditions, and we will work together to speed up their legal transfer to Europe," Tsipras said.

dj/kms (dpa, AP, Reuters, MIA)