Kiev on Thursday accused a Russian air force jet of shooting down a Ukrainian warplane over its territory Wednesday, ratcheting up tensions along the volatile border between the two ex-Soviet states.
"A military plane from the air force of the Russian Federation carried out a rocket strike on a Ukrainian airforce SU-25 as it fulfilled its task over the territory of Ukraine," Ukraine's National Security and Defence Council said on Twitter.
The pilot of the downed fighter jet managed to eject and was later evacuated by Ukrainian forces, the military said.
The latest allegation from Kiev comes after it said that a military transport plane downed Monday was "likely" hit by a missile fired from the Russian side of the porous border.
A spokesman for the security council confirmed Thursday that two of the eight crew members on board died in the incident, while another four have been rescued and two were captured by pro-Russian rebels.
Tensions along the frontier -- across which Ukraine says Russia is pouring fighters and weapons to fuel the separatist uprising -- are at boiling point, with Kiev warning that Moscow has massed thousands of troops there in preparation for a possible invasion.
The US and EU on Wednesday slapped tougher sanctions on Moscow in a bid to force the Kremlin into pressuring pro-Russian rebels into ending a three-month insurgency that has claimed more than 600 lives.