Ukrainian president decries 'direct and open aggression' by Moscow

Ukrainian military officials on Monday pulled their forces from defending a strategic airport in the east against pro-Russian rebels – the latest in a string of reverses for Ukrainian forces – as President Petro Poroshenko accused Russia of "direct and open aggression."

"Direct and open aggression has been launched against Ukraine from a neighboring state,” Poroshenko said during a speech at a military academy in Kiev. “This has changed the situation in the zone of conflict in a radical way."

Ukrainian National Security Council spokesman Col. Andriy Lysenko said Ukrainian forces had been ordered to retreat from the airport in Luhansk, the second-largest rebel-held city, in the face of an intensifying assault that he blamed on "professional artillery gunmen of the Russian armed forces."

Russia consistently denies allegations that it has sent troops or equipment into Ukraine. But Lysenko said Monday that "not less than four battalions and tactical groups of the Russian armed forces are active in Ukraine."

Meanwhile, Russian Foreign Minister Sergei Lavrov called for an unconditional cease-fire in the Belarusian capital of Minsk, amid talks on the crisis in eastern Ukraine.

In the past week, the rebels have opened a new front along the southeastern Azov Sea coast and are pushing back after Ukraine had appeared close to crushing the four-month rebellion in the east, which erupted after a pro-Moscow president was forced out of power by popular protests.

Lavrov earlier Monday said Russia would not intervene militarily in Ukraine, defying reports by Poroshenko and his administration, NATO and Western nations that Russia has already sent troops, artillery and tanks across Ukraine's southeast border to reinforce the separatists.

"There will be no military intervention," Lavrov told students at Moscow State Institute of International Relations. "We call for an exclusively peaceful settlement of this severe crisis, this tragedy."

The envoys to Monday’s meeting in Minsk, who last met in July, included representatives of Ukraine, Russia and the Organization for Security and Cooperation in Europe (OSCE). A separatist leader, Andrei Purgin, also was to take part.

Purgin told the Interfax news agency that the separatists' priority was to win recognition of their independence in eastern Ukraine, which has a large Russian-speaking population. He said they also were willing to discuss the exchange of prisoners and a temporary cease-fire.

Russian President Vladimir Putin, who called on Sunday for immediate negotiations on the "statehood" of southern and eastern Ukraine, blamed Kiev's leadership for refusing to enter into direct political talks with the separatists.

Putin also hoped "common sense" would prevail in the West over the possibility of imposing additional economic sanctions, despite Moscow's denials that it is helping the rebels.

Putin's use of the word "statehood" was interpreted in Western media as implying backing for the rebel demand of independence, something Moscow has so far stopped short of publicly endorsing.

However, Putin's spokesman Dmitry Peskov said there was no new endorsement from Moscow for rebel independence. Asked if "New Russia," a term pro-Moscow rebels use for their territory, should still be part of Ukraine, Peskov said: "Of course."

"Only Ukraine can reach an agreement with New Russia, taking into account the interests of New Russia, and this is the only way to reach a political settlement."

The United States and European Union have gradually tightened economic sanctions against Russia, first imposed after Moscow annexed Ukraine's Crimea peninsula in March.

“Russia is already more isolated than at any time since the Cold War,” President Barack Obama said at a White House press conference Thursday.

Al Jazeera and wire services