IDOMENI, Greece — Migrants waged running battles with Macedonian police Sunday after they were stopped from scaling the border fence with Greece near the border town of Idomeni, and aid agencies reported that hundreds of stranded travelers were injured.

Macedonian police used tear gas, stun grenades, plastic bullets and a water cannon to repel the migrants, many of whom responded by throwing rocks over the fence at police. Greek police observed from their side of the frontier but did not intervene.

More than 50,000 refugees and migrants have been stranded in Greece since Balkan countries closed their borders to the massive flow of refugees pouring into Europe. Around 11,000 remain camped out at the border with Macedonia, ignoring instructions from the government to move to organized shelters as they hold out hope to reach Western Europe.Clashes continued in the afternoon as migrant groups twice tried to overwhelm Macedonian border security.

The increasing use of tear gas reached families in their nearby tents in Idomeni’s makeshift camp. Many camp dwellers, chiefly women and children, fled into farm fields to escape the painful gas.

Observers held out hope that evening rainfall, which began about seven hours into the clashes, would dampen hostilities.

The aid agency Doctors Without Borders estimated that their medical volunteers on site treated about 300 people for various injuries. Achilleas Tzemos, deputy field coordinator of Doctors Without Borders, said the injured included about 200 experiencing breathing problems from the gas, 100 others with cuts, bruises and impact injuries from nonlethal plastic bullets.

Macedonian police said 23 members of the country’s security forces were injured, including 14 police officers and nine soldiers.