Ukrainian security officers arrested two people suspected of acting on behalf of Russia as they tried to blow up a railway line used to supply weapons to the east for Kyiv's war effort, the Security Service of Ukraine (SBU) said on Tuesday.

The detainees, identified only as residents of the Kyiv and Kharkiv regions, planted an explosive device by the line in central Poltava region and planned to detonate it remotely, but they were caught red-handed by SBU officers, the statement said.

There was no immediate comment from Russia.

"The occupiers hoped to ruin logistic routes for weapons, ammunition and fuel for the Ukrainian armed forces," the SBU said.

It confiscated the phones of the detainees, it said, and identified their handler as an officer of Russia's main domestic intelligence agency, the Federal Security Service (FSB).

The bomb was meant to be detonated during Russian airstrikes that pounded critical infrastructure on March 21-22, it added.

Russia stepped up its strikes last week, ramping up the pressure on Ukraine more than two years since Moscow launched its full-scale invasion.

  - Reuters