Humanitarian groups have sounded the alarm over the fate of thousands of civilians caught in clashes between Myanmar’s army and rebel fighters in northern Kachin state, the UN said Friday.

Conflict in Kachin along the border with China has displaced 100,000 people since a 17-year ceasefire collapsed in 2011, and a new peace deal has proved elusive, with skirmishes spilling into neighbouring Shan State.

Heavy fighting near several displacement camps in southern Kachin caused 2,700 people to flee in April, according to the UN’s Office for the Coordination of Humanitarian Affairs (OCHA), which said there was a “deteriorating security situation” in the region.

“Humanitarian organisations remain seriously concerned by an increase in insecurity and the displacement of thousands of people over the past weeks in southern Kachin State and northern Shan State,” it said in a statement.

Many of those displaced have been made homeless for the second or third time, while an unknown number of people are thought to have fled across the border into China.

Ethnically-diverse Myanmar has suffered the longest-running civil war in the world, with multiple insurgencies in its minority borderlands that flared soon after independence from British colonial rule in 1948.

A quasi-civilian regime that replaced outright military rule in 2011 has signed ceasefires with 14 of the 16 major armed ethnic groups, but conflict continues with the Kachin Independence Army (KIA) and Ta’ang National Liberation Army (TNLA) in Shan state.

A fresh round of talks with the KIA’s political wing this week produced little progress besides an agreement on further dialogue.

Observers say that broad peace talks with all major ethnic minority groups set for May 19 and 20 have been postponed by two days because of increased tensions in Kachin and Shan.

“We are trying to reduce suspicion from both sides,” Hla Maung Shwe, a senior official at the Myanmar Peace Center negotiating body, told AFP.

More than 50 percent of those displaced in Kachin are in camps beyond government control, with limited help from international aid groups.

“The approaching rainy season will bring higher risks of flooding and water-borne diseases, so water, sanitation, and hygiene will increasingly be a priority in humanitarian interventions over the next weeks,” said Florent Turc, Field Coordinator for Solidarites International in Kachin, in the OCHA statement.