Russia has suffered one of its worst aerial disasters of the Ukraine war, as an An-26 Military Transport aircraft went down in Crimea with no survivors reported.

The aerial disaster happened Tuesday, with state media reporting that the aircraft slammed into a cliff during what was described as a routine flight over the Black Sea peninsula.

All 29 onboard, including 23 passengers and six crew, were killed in the crash, marking one of the deadliest recent incidents involving Russian military aviation in the region.

Officials say the trouble began very quickly into the flight. "On 31 March at around 18:00 Moscow time, contact was lost with the An-26 military transport aircraft whilst it was on a scheduled flight over the Crimean Peninsula," the defense ministry said.

Shortly after, confirmation came from the ground: "The An-26 aircraft, with which communication was lost earlier, crashed into a cliff, it was reported to TASS from the site of the crash."

While no official cause has been confirmed, early indications point to possible technical failure, which if accurate would mark another blow to aging Soviet-era hardware still widely used across Russia’s military fleet, also as sweeping Western sanctions have been in effect, impacting aviation parts and software.

A huge search effort for bodies is ongoing and is difficult, given the crash happened in a mountainous region. Various emergency units - local and national - are involved.

Meanwhile, separately there are reports of a new drone attack on a Russian petrochemical plant:

"A criminal case was opened into the crash of the aircraft due to alleged violations of Article 351 of the Russian Criminal Code which pertains to violations of flight rules or regulations governing flight preparation, according to a report from the Russian Investigative Committee press office," one regional report says.