Russian Foreign Minister Sergei Lavrov on Monday invited the Organization for Security and Co-operation in Europe (OSCE) to send observers to monitor two of its Russian-Ukrainian border crossings - Gukovo and Donetsk.

"In connection to the worsening situation in the region where Kyiv is carrying out its military operation in the southeast of Ukraine, the Russian side, in the order of goodwill and without waiting for a ceasefire is inviting OSCE observers to check points...on the Russian-Ukrainian border," the Foreign Ministry said in statement.

Meanwhile, Ukraine's defense minister on Monday said that a Ukrainian AN-26 military transport plane had been shot down by a rocket which was "probably" fired from Russian territory. The plane was taking part in the military campaign against separatist rebels.

Rebels in conflict-wracked eastern Ukraine had earlier claimed responsibility for the attack.

Defense Minister Valeriy Heletey, however, said the rocket was flying at an altitude too high to be reached by the weapons used by the separatist pro-Russia rebels.

Authorities say the plane may have been carrying around 20 people but there was no immediate word on casualties.

Intense fighting in Luhansk

Fighting intensified Monday around Luhansk, which is controlled by pro-Russia separatists. TheUkrainian defense ministry said that its forces had retaken several villages around the city, while at the same time breaking through a rebel blockade and reopening a corridor to the city's airport.

The rebels, though, rejected claims that government forces were now actually in control of the airport.

The pro-Russia separatists, however, did concede that 30 of their fighters had been killed after coming under fire in Alexandrovka, in the east of Luhansk. The defense ministry in Kyiv confirmed that its warplanes had carried out five airstrikes on Sunday.

"The enemy suffered significant losses," the ministry said, without putting a figure on the casualties. This, it was reported, included a strike on an armored convoy, which Kyiv said had crossed into Ukrainian territory.

hc/kms (Reuters, AP)