"A bus accelerated to pass a car which was crushed under the bus and caught fire," said police lieutenant colonel Min Aung of the Myanmar Police Force headquarters in the capital Nay Pyi Taw.
Six people on the bus, which was travelling from eastern Shan State to Yangon, were killed and four were injured, while six car passengers died, he said.
The crash happened in the early hours of the morning on a road that connects Mandalay and Yangon via Nay Pyi Taw. The road has been dubbed the "death highway" by local media due to frequent traffic accidents.
The concrete road was built hastily by the former junta after the generals in 2005 suddenly moved the capital from Yangon to the new purpose-built city in central Myanmar.