The Chinese-built Y-12 had taken off from the southern airbase of Wirawila and was heading to Ratmalana, south of Colombo, when it crashed, spokesman Chandana Wickramasinghe said.
"We are still investigating the cause of the crash," Wickramasinghe said, adding that all four officers on the plane were killed in the crash at Haputale, 200 kilometers (125 miles) east of Colombo, AFP reported.
It was the worst air crash in Sri Lanka since an AN-32 military transport plane came down just outside the capital in December 2014 killing all five crew onboard.