Updated

The Bellingcat investigative group says that it has identified nine Russian officers who allegedly were directly involved in the rocket attack on an eastern Ukrainian city that killed at least 30 civilians.

The group, which has previously released reports on the conflict in eastern Ukraine and the fatal downing of a Malaysian airliner over rebel-held territory, says it analyzed video and audio data that Ukraine is providing to the International Court of Justice.

Mariupol, a strategic port city on the Azov Sea, came under rocket fire on Jan. 24, 2015. Separatist rebels initially announced they were advancing on the city, then backtracked and blamed Ukrainian forces.

Russia persistently denies allegations of supporting separatist rebels in Ukraine. The Defense Ministry didn't respond to a request for comment on Monday's report.