YANGON, Aug. 18 (Xinhua) -- Armed groups have continued to attack Lashio, the biggest city in Myanmar's northern Shan state, with heavy arms firing on the government forces and police stations, the Office of the Commander-in-Chief of the Defense Services said.

The attacks launched Friday night by the Arakan Army (AA), Ta'ang National Liberation Army (TNLA) and Myanmar National Democratic Alliance Army (MNDAA), destroyed bridges on Hsenwi-Kunlong road and burned a petrol station on Lashio-Hsenwi road, the military said in a statement released late Saturday.

During the night, the combined armed groups also fired three rocket propelled grenades on a battalion headquarters in Kyaukme, Shan state and retreated to the west after being fired back by the armed forces.

The groups also mined two reinforced concrete bridges of Byone Taung on Namt Slup-Kunlong road and Mantonsun on Hsenwi-Namt Slup road before dawn on Saturday.

The military columns conducting security operations around Kutkai-Namtpatkha-Muse region also encountered with the armed groups until Saturday morning. In the armed groups' heavy arms attacks, a vehicle from a local philanthropic association from Lashio was hit with one being killed.

In a mine clearance operation around Gote Twin bridge sabotaged by the armed groups, 33 improvised explosive devices with half ton of explosives, 22 detonators and grenades were defused.

The coordinated attacks of the combined armed groups, which started in the early hours of Thursday by firing artillery shells at five places in Mandalay region and Shan state, have killed 15 people with 13 others injured.

The deaths include three civilians, three policemen and nine military personnel while the injured include 10 civilians, two police personnel and one military serviceman, said U Zaw Htay, spokesman of Myanmar President's Office.