By Agence France-Presse
Eight coaches and the engine of the Jagdalpur-Bhubaneswar express derailed at 11:00 pm (1730 GMT) near Kuneru railway station in Vizianagram district of Andhra Pradesh state.
"The death toll has risen to 23. Many people are injured," J. P. Mishra, a spokesman for East Coast Railways told AFP.
"The injured have been shifted to two nearby hospitals and doctors from railways are attending to them," he said.
Officials from the railway and local government were carrying out rescue work and relief trains had been sent to evacuate passengers, he said.
He did not immediately give a cause for the derailment or the number of passengers affected.
The train was travelling from Jagdalpur city to Bhubaneswar, the capital of Odisha state, when it came off the track nearly 160 kilometres (100 miles) from Visakhapatnam, the nearest city to the accident site.
Thirteen of the train's 22 coaches were unaffected in the incident.
Rail traffic on the coast line has been suspended.
India's railway network is still the main form of long-distance travel in the vast country, but it is poorly funded and deadly accidents occur relatively frequently.
On Friday 10 coaches of an express train were derailed in western Rajasthan state leaving many passengers with minor injuries.
The latest deadly incident comes two months after 146 people were killed when a passenger train was derailed in Kanpur, northern India, in one of the country's worst rail disasters.
Last month two people were killed and dozens injured after another train derailed also near Kanpur, Uttar Pradesh state.
In 2014, an express train ploughed into a stationary freight train, also in Uttar Pradesh, killing 26 people.
A 2012 government report said almost 15,000 people were killed every year on India's railways and described the loss of life as an annual "massacre".
Prime Minister Narendra Modi's government has pledged to invest $137 billion over five years to modernise the crumbling railways, making them safer, faster and more efficient.
The government has signed numerous deals with private companies to upgrade the ageing network.
Japan has agreed to provide $12 billion in soft loans to build India's first bullet train, though plans remain in their infancy.