BANGKOK (AP) — A drone attack on a police headquarters in a major border town in eastern Myanmar has killed at least five officials including a senior army officer and a district administrator, members of two emergency rescue teams and media reports said Monday.

The attack, carried out Sunday evening in two stages, is believed to be the deadliest aerial bombing targeting high-ranking security and administrative officials since armed resistance was launched more than two years ago against the military that seized power in February 2021 from the elected government of Aung San Suu Kyi.

The takeover was met with peaceful nationwide protests, but after security forces cracked down with lethal force, many local armed resistance groups were formed and loosely organized into what is called the People’s Defense Force, or PDF. It's the armed wing of Myanmar’s shadow National Unity Government, which views itself as a country’s legitimate administrative body.

The PDF has allied themselves with major ethnic guerrilla groups in border regions that have been carrying out armed struggle against the army for decades, seeking greater autonomy.

Federal Wings, a resistance group that conducts drone warfare in cooperation with the People’s Defense Force and its allies belonging to ethnic Karen armed groups, claimed responsibility for Sunday’s attack in a statement posted Monday on their Facebook page. The group also said it learned that five people, including the battalion commander, had been killed.

Lt. Col. Aung Kyaw Min, the temporary commander of a battalion based in Myawaddy township, and ​a traffic police officer died Sunday in a hospital after the attack, said two rescue workers, speaking on condition of anonymity because they feared arrest for disclosing the information.

Myawaddy District Administrator Soe Tint, his aide-de-camp Tun Tun Nyein and a clerk died on the spot when drones dropped two bombs while they were inspecting the damage caused by a drone attack about an hour earlier, they said. The district police office compound is located in downtown Myawaddy, a key trading center in southeastern Kayin state on the border with Thailand.

They added that 10 security and administrative officials were being treated in township and military hospitals in Myawaddy while four others including the head of the district police office were sent to a private hospital in Mae Sot, just across the border in Thailand, which had better medical care. One of the rescue workers said he was informed that a police officer there became the sixth fatality on Monday, but the death could not be confirmed.

The military information office, the Tatmadaw True News Information Team, said in a statement that some members of security forces and civil servants were injured after the Karen National Liberation Army and the People’s Defense Force dropped two bombs from a drone. It did not acknowledge any deaths.

Drones have become crucial for the resistance forces, which are outmanned and outgunned by the military that's carried out airstrikes unimpaired. Initially, smaller drones with lighter payloads were used, but now the opposition groups are using more sophisticated systems to drop explosives precisely on military targets.

The statement by Federal Wings claiming responsibility for the attack included a warning to civil servants and their family members to leave government offices and housing and advised Myawaddy residents to stay away from the official offices and military outposts for their own safety. It said that their sole targets were armed security forces working for the military.