With the world's attention focused on Iraq, it's easy to forget that the Ukrainian government is still trying to recapture territory taken by separatists. Some obsolete tanks rolled into southern Ukraine on Friday bound for use by the rebels. The Russian government denies they sent them - and they did it with a straight face.

But a real escalation of the violence occurred yesterday when rebels shot down a military transport as it was attempting to land. Forty nine Ukrainians lost their lives in the attack.

Reuters:

"All those involved in cynical acts of terrorism of this magnitude must be punished," he said, declaring Sunday a day of mourning for the nine crew and 40 paratroopers killed.

He later issued a separate statement saying he had called another meeting of his security chiefs for Monday, and that the armed forces had already intensified their operation - intended to prevent Ukraine breaking up.

"For the sake of peace, we will act decisively and purposefully," he said, hailing the seizure of the port city of Mariupol from the rebels on Friday and the recapture of 248 km (155 miles) of the frontier with Russia "across which the terrorists get weapons, equipment, reinforcements and money."

Charred debris was scattered for hundreds of meters (yards) over the sloping wheat field where the plane came down near Novohannivka, a village 20 km (12 miles) southeast of Luhansk.

The tail section jutted up from the ground, with pieces of the engines, fuselage and other parts lying around it. A platoon of rebel forces in camouflage scoured the ruins for ammunition.

"This is how we work. The fascists can bring as many reinforcements as they want, but we will do this every time. We will talk to them on our own terms," said a stocky 50-year-old rebel who identified himself as Pyotr, his 'nom de guerre'.

He had an assault rifle in one hand, a light machine gun in the other and two ammunition belts round his neck.

The death toll was the highest suffered by government forces in a single incident since the crisis flared in February and is likely to fuel tension between Russia and Kiev's main ally, the United States, which accuses Moscow of arming the rebels.

In a telephone call with Ukrainian Prime Minister Arseny Yatseniuk, U.S. Secretary of State John Kerry expressed condolences for the servicemen's deaths, a senior State Department official said.

Kerry also spoke to Russian Foreign Minister Sergei Lavrov and warned him that the United States and its G7 partners would "raise the costs" Moscow could face unless it curbed weapons supplies into Ukraine and cut ties with the separatists.

Where did the rebels get anti-aircraft missiles? If Russia supplied them, they must have expected the separatists to use them. And that raises the stakes in the region, as the Ukraine government must now escalate to respond to the attack.

President Putin seems content to keep the conflict at a low boil - not provoking a more determined response from the west but preventing the Ukranian government from winning back territory taken by the separatists. With America preoccupied with events in Iraq, Putin must think he can get a pass on keeping the fires burning in Ukraine.