UKRAINIAN President Petro Poroshenko accused Russia today of “direct and open aggression” which had pushed Kiev forces onto the back foot in their fight against rebels in the country’s east.

Ukraine’s military has been forced to order its troops to pull back from a vital airport near the city of Lugansk and the Kiev-based prime minister is desperate not to admit that his forces are being defeated militarily by the rebels.

Mr Poroshenko also turned on his own senior military staff, saying there would be high-level personnel changes in the Ukrainian armed forces after troops fled a new rebel advance in the south.

Meanwhile, Russian President Vladimir Putin attacked Kiev’s leadership for refusing to enter into direct political talks with its opponents.

“The current Kiev leadership does not want to carry out a substantive political dialogue with the east of its country,” he warned.

President Putin also said the rebels were trying to force Ukrainian troops from positions where they were firing on civilian targets.

“The aim of the militia fighters is to push away these armed forces and their artillery to not give them the possibility to shoot on residential areas,” he said.

Until last week, Ukraine had appeared close to crushing the four-month rebellion in the east.

But then the rebels opened a new front to the south, pushing towards the city of Mariupol.

Elsewhere, Nato leaders pondered creation of a high-readiness force and the stockpiling of military equipment and supplies in eastern Europe to protect member nations there against alleged Russian aggression.

“The Readiness Action Plan will ensure that we have the right forces and the right equipment in the right place, at the right time,” Nato secretary-general Anders Fogh Rasmussen said.

“We will do what it takes to defend our allies.”

Mr Rasmussen said the proposed new force could be composed of several thousand troops.

Backed by air and naval assets, the unit would be a “spearhead” that could be deployed at very short notice to help Nato members defend themselves against any threat, including Russia, Mr Rasmussen said.