Pro-Russian gunmen shot down a Ukranian military transport plane Saturday in the separatist east, killing all 49 people on board in the biggest single loss of life in the two-month insurgency.

“The terrorists cynically and treacherously fired with a large-caliber machinegun hitting an Ilyushin-76 of the Ukrainian air force which was carrying troops on rotation and was about to land at Lugansk airport,” the ministry said in a statement.

The four-engine jet was also carrying “equipment.”

The ministry offered its condolences to the families of the “killed soldiers,” but did not say how many died.

Lugansk, which is close to the Russian border, is the main city of one of two eastern regions hit by pro-Moscow separatist violence and which has declared its independence from Kiev.

An “anti-terrorist” clampdown by Ukrainian armed forces has left at least 270 people dead over the past two months.

The attack came less than a week after the rebels fighting Ukraine’s Western-backed government launched attacks on Lugansk International Airport.

The assaults, which took place Saturday evening and Sunday morning in the immediate wake of the inauguration of Ukraine’s new President Petro Poroshenko, did not result in any injuries among the defenders.

But one of the Ukrainian paratroopers guarding the airport told AFP at the time it was clear the rebels were trying to destroy the building which controls the power supply to the airport.

The United States on Friday accused Russia of sending tanks and rocket launchers to pro-Moscow rebels in Ukraine as Kiev’s resurgent forces hoisted the national flag over a strategic rebel-held port amid fears of possible Russian gas cuts.

Moscow said Ukrainian tanks had crossed the border into its territory before being intercepted, a day after Ukraine alleged that three tanks had crossed from Russia into its territory, underscoring the growing tensions between Kiev and Moscow.

Poroshenko told his Russian counterpart Vladimir Putin that the tanks’ crossing into the former Soviet republic’s separatist east was “unacceptable.”

Washington backed Kiev’s claims, saying separatists in eastern Ukraine had also obtained multiple rocket launchers from Russia among other heavy weapons and military equipment.

The United States has “information that Russia has accumulated tanks of a type no longer used by Russian forces at a deployment site in southwest Russia, and some of these tanks recently departed,” State Department deputy spokeswoman Marie Harf said Friday.

“We are confident that these tanks came from Russia,” she added, noting that no Ukrainian tank units have been operating in the area.

Earlier, she told reporters that a convoy of three T-64 tanks, several BM-21 or Grad multiple rocket launchers and other military vehicles had “crossed from Russia into Ukraine.”
Internet videos had shown the same types of tanks moving through multiple cities in eastern Ukraine, including Snizhne, Torez and Makiyivka, Harf said.

The same types of rocket launcher were seen travelling through Lugansk.

NATO chief Anders Fogh Rasmussen warned that reports of pro-Russian groups acquiring heavy weapons from Russia, including tanks, would mark a “serious escalation” of the crisis if confirmed.

Poroshenko celebrated the “heroism” of soldiers hoisting the national flag over the strategic rebel-held port of Mariupol.

He proclaimed the industrial Sea of Azov city the new temporary capital of Donetsk — an eastern rustbelt region overrun by pro-Russian gunmen for the past two months.

Mariupol has wavered between rebel and Kiev control for weeks and was also the scene of pitched battles on May 9 that killed more than a dozen people.