Ships and planes were scouring the coast of southern Myanmarafter a military aircraft vanished over the Andaman Sea, the army and civil aviation officials said.
The plane was carrying 122 soldiers, family members and crew.
The Chinese-made Y-8-200F transport plane left the coastal town of Myeik at 1.06pm, heading north to Yangon, Myanmar's largest city, officials said.
It was on a weekly military flight that was scheduled to stop at several coastal towns along the way.
The plane lost contact 29 minutes after takeoff while flying at 5,485m over the sea, about 70km west of the town of Dawei, the military said.
"We don't know what exactly happened to this plane after the loss of contact," said Kyaw Kyaw Htey, a civil aviation official at Myeik airport.
The latest military update put the total number of those aboard at 122; including 108 soldiers and their family members and 14 crew.
Among the passengers were 15 children, 58 adults and 35 soldiers and officers, according to the statement.
It is monsoon season in Myanmar, but Kyaw Kyaw Htey said the weather had been "normal" with good visibility when the plane took off.
The military began a search soon after the plane disappeared, mobilising nine navy ships and three military planes, the army said in its latest news release. The search continued as darkness fell.
Some 300 to 400 people, including firefighters, medics, emergency and welfare officials, gathered on the shore near the town of Launglon, close to the area where the naval search was concentrated, said Naing Myo Thwin, the chairman of the local funeral association, from the scene.
Aung Win, a local police officer also speaking from the scene by telephone, confirmed that a large number of people had gathered on the beach. He said because no trace of the plane had been found, so they were moving to other areas along the shore.
The aircraft was bought in March 2016 and had a total of 809 flying hours. It was carrying 2.4 tons of supplies, the military said.
Aircraft incidents, both civilian and military, are not uncommon in the Southeast Asian country. A military helicopter crashed last June in central Myanmar, killing three military personnel on board.
Five military personnel were killed last February after an air force aircraft crashed in the countryG��s capital, Naypyitaw, according to media reports. Two people were killed and 11 injured after a small plane crashed in central Myanmar in 2012.
- Reuters / BBC