Twin bomb blasts inside a train in the southern Indian city of Chennai have killed at least one person and injured nine.
The low-intensity explosions took place in two carriages as an express train travelling from Bangalore in the south to Guwahati in the north-east arrived at the Chennai station on Thursday morning.
"A young lady, aged 22, has lost her life. There were two separate blasts in the train. The entire police force is involved in the investigation," senior railway official Rakesh Mishra told reporters.
Two of the injured are in critical condition, local reports have said.
The woman, travelling from Bangalore to Vijayawada, was killed instantly when a bomb went off under her seat, local authorities said.
Mallikarjun Kharge, India's railway minister, said these were minor intensity blasts and experts from Delhi are being sent to investigate the attack.
Indian authorities had tightened security measures across the country with the month-long elections to the lower house of parliament taking place.
No one has claimed responsibility for the attack, but news channel NDTV reported a man hiding in one of the compartments has been taken into custody and is being questioned.