US-led military exercises due to begin in western Ukraine

A soldier from the Ukrainian self-defence battalion "Azov" talks to a car driver at a checkpoint in the southern coastal town of Mariupol, Sept 8, 2014. [Photo/Agencies]

'Breaking the rules'

"From our side, nobody is shooting but they are breaking the rules, everybody in the world knows it," said a rebel commander defending a checkpoint near a village south of Donetsk.

The simmering crisis has exposed layers of mistrust between the West and Moscow and between the largely Russian-speaking populations in the east of Ukraine and the pro-Western leaders in Kiev.

The truce halted a rebel counter-surge across the southeast last month with the alleged support of Russian paratroopers and heavy weaponry that turned the tide of the war against Ukrainian forces.

NATO and Kiev say at least 1,000 Russian soldiers and possibly many more remain on Ukrainian soil although the Kremlin denies this.

Prime Minister Arseniy Yatsenyuk accused Russian President Vladimir Putin on Saturday of seeking to "eliminate" Ukraine as an independent country with the goal of resurrecting the Soviet Union.

Poroshenko heads to Washington this week to meet US President Barack Obama, seeking to secure a "special status" with the United States as he steers Ukraine further out of Russia's orbit.

Obama has rejected direct military involvement but unveiled tougher economic sanctions on Moscow that - together with similar EU measures - effectively lock Russia out of Western capital markets and hamstring its crucial oil industry.

Russian Foreign Minister Sergei Lavrov accused Washington of trying to use the crisis to "break economic ties between the EU and Russia".

The punitive measures and an accompanying East-West trade war have left Russia's economy facing possible recession but have seemingly failed to alter Putin's course.

Badly needed aid

Russia on Saturday sent a 220-truck convoy it said was carrying aid to the residents of rebel-held Lugansk, who have been struggling without water and power for weeks.

Ukraine - which did not give permission for the convoy to cross - had expressed fears the trucks may be carrying supplies for insurgents and bitterly protested a similar delivery last month.

On the domestic front, cracks emerged in Poroshenko's administration when a deputy foreign minister quit over a delay in the implementation of an EU trade deal, apparently under Russian pressure.

Meanwhile the pro-Russian Regions Party that ruled Ukraine under ousted president Viktor Yanukovych also announced Sunday it would boycott the Oct 26 parliamentary ballot and form an "opposition government" designed to fight Kiev's westward course.