A Ukrainian military intelligence officer was killed by a bomb under his car while he was driving through the country's capital, Kiev, officials say.
The victim has been named as Col Maxim Shapoval. His car was destroyed and two passers-by were slightly injured.
Officials said the incident was a "terrorist act".
No motive has been suggested but analysts say it may be connected to the Russian-backed insurgency in eastern Ukraine.
The explosion happened as the Mercedes was moving at around 08:00 local time (05:00 GMT), police said.
"At the present time the picture gathered of the crime suggests it was a planned terrorist act," Interior Ministry spokesman Artem Shevchenko said, without giving details of who they believed was behind the attack.
It is the latest in a series of attacks in Kiev. In March, former Russian MP Denis Voronenkov, a critic of President Vladimir Putin, was shot dead outside a hotel in the capital.
And last July, a prominent investigative Belarusian journalist and also a Kremlin critic, Pavel Sheremet, was killed by a bomb in his car in the capital.