Convoy delivering humanitarian aid came under fire in northeastern Shan State but escaped unharmed.

Singapore said two staff from its embassy in Yangon were part of the convoy that came under fire on Sunday, and had returned safely to the city.

“Singapore condemns this attack,” the city-state’s Ministry of Foreign Affairs said in a statement late on Monday. “It is critical to safeguard the safety of humanitarian and diplomatic personnel, to ensure that they can continue their operations and provide necessary aid to those in need.”

It was not clear who was behind the attack, which Indonesia’s President Joko Widodo said took place as the officials were on their way to “hand over humanitarian aid” in the region. The United States, in emailed comments, said the convoy was under military escort.

“Regretfully on their way, there was a shootout,” Widodo was quoted as saying by the AFP news agency.

Indonesia this week hosts the ASEAN summit in eastern Labuan Bajo with the 10-member group of Southeast Asian nations under increasing pressure over its failure to do more to resolve the crisis in Myanmar triggered by the February 2021 coup.

The military has ignored the so-called Five Point Consensus that coup leader Min Aung Hlaing agreed with ASEAN in April of that year, and is battling armed resistance groups as well as long-established ethnic armed organisations in a situation some have described as civil war.

Thousands have been killed, and more than a million civilians have been forced to flee.

“Singapore urges all parties to refrain from violence, in accordance with the Five-Point Consensus,” Singapore’s statement continued. “Only constructive dialogue among all key stakeholders in Myanmar can facilitate a peaceful solution in the interests of the people of Myanmar.”

The US State Department also expressed its concern at the incident.

“These attacks in Shan State come as the regime’s violence and disregard for the rule of law have led to greater instability on the ground, all while the regime has continued to neglect its commitments under the ASEAN Five-Point Consensus, including ceasing its violence and enabling unhindered humanitarian access,” said department spokesperson Matthew Miller.

The statement urged the military to “respect the democratic aspirations of the people who have demonstrated they do not want to live another day under the military’s tyranny” and abide by its obligations under international humanitarian law, including rules on the protection of diplomatic personnel and civilians.

State-run television reported the attack was the work of “terrorists”, which is the word the military uses to describe all its opponents.

The National Unity Government (NUG), set up by elected officials overthrown in the coup, also condemned the incident saying such attacks were “contrary” to its principles.

“This attack is neither ordered nor condoned by the NUG or by its partners,” it said in a statement. The NUG has established a network of People’s Defence Forces to fight against military rule.