ODESA, Ukraine -- An overnight explosion near the Black Sea port city of Odesa has damaged a rail line and delayed trains for hours but reportedly did not cause any injuries.
The Ukrainian Interior Ministry said on May 13 that the blast, which occurred around midnight, left a meter-deep crater under the tracks.
Officials say train transport was resumed by morning rush hour.
An investigation has been launched into what authorities described as an act of "sabotage."
On May 12, also in Odesa, local law enforcement officials said they had found and defused an explosive device planted very near a natural-gas pipeline leading to a machine-building factory.
A city of 1 million people, Odesa lies less than 450 kilometers from Kyiv and hundreds of kilometers from the battle lines between central government forces and pro-Russian fighters who declared "people's republics" in eastern Ukraine.
But it was the scene a year ago of one of the deadliest civilian incidents since conflict erupted in eastern Ukraine, with more than 30 pro-Russians found dead after a fire swept through a trade union building where they reportedly sought refuge from a hostile crowd.
Last month, the Ukrainian Security Service (SBU) announced that it had detained more than 40 suspected members of a terrorist group in Odesa who allegedly were planning a series of attacks in the city during celebrations marking the Orthodox Easter on April 12.
Also in April, the SBU detained three people suspected of involvement in a series of bombings in Odesa, some of them targeting organizations with ties to soldiers fighting against Russian-backed rebels in eastern Ukraine, where more than 6,100 people have been killed since April 2014.
There have been a number of explosions in recent months in Odesa and the eastern city of Kharkiv, Ukraine's second-largest city.
In February, a policeman, an activist, and a teenager were killed in Kharkiv when an explosion ripped through a march marking the first anniversary of the Maidan antigovernment protests in Kyiv that ousted pro-Russian President Viktor Yanukovych in 2014.
Officials have blamed the blasts on Russia and pro-Moscow rebels who hold parts of the eastern provinces of Donetsk and Luhansk.