PETER LEONARD
Associated Press

KIEV, Ukraine (AP) — NATO’s chief defied mounting Russian belligerence Thursday with a pledge to provide assistance to Ukraine, which is battling to quash an insurgency being waged by pro-Russia rebels in the country’s east.

The show of support from Anders Fogh Rasmussen comes as government troops increasingly focus their push to claw back rebel-held territory on the stronghold of Donetsk. Ukraine appears to be ratcheting up the urgency of its onslaught against the backdrop of an alleged escalation of Russian troop presence on the border.

“In response to Russia’s aggression, NATO is working even more closely with Ukraine to reform its armed forces and defense institutions,” Rasmussen said during a visit to the Ukrainian capital, Kiev.

In a sign of sagging morale among rebel forces, separatist authorities issued a desperate plea for assistance Thursday, complaining in a statement that a “critical situation has developed with the militia’s food, uniform and ammunition supplies.”

In Donetsk, sustained shelling struck residential buildings and a hospital, killing at least four people and wounding 10 others, local officials said.

Mortar fire struck the Vishnevskiy Hospital on Thursday morning, killing one and wounding five others, Donetsk city council spokesman Maxim Rovensky told The Associated Press.

“There was a sudden explosion,” witness Dr. Anna Kravtsova said. “A mortar round flew through the window.”

The shelling, which destroyed an array of equipment in the dentistry unit, also hit three nearby apartment buildings.

It followed a night of shelling in another neighborhood as the fighting between the government and pro-Russian separatists is inching ever closer to the city center. The mayor’s office said in a statement posted on its website that three people had been killed, five wounded and several residential buildings destroyed during those attacks.

The government denies it uses artillery against residential areas, but that claim has come under substantial strain in the face of mounting evidence to the contrary.

Pro-Russian separatists in eastern Ukraine have been fighting the Kiev government since April. Ukraine and Western countries have accused Moscow of backing the mutiny with weapons and soldiers. The West accused Russia of most likely providing the insurgents with surface-to-air missiles that may have been used to shoot down a Malaysia Airlines passenger jet over rebel-held territory on July 17, killing all 298 people on board.

The Russian government has repeatedly denied all those charges.

More recently, Moscow has drawn accusations it is attempting to sow more instability with an intimidating show of force by dispatching what NATO estimates is 20,000 troops to Ukraine’s eastern border. That deployment has led many to speculate Russia may pursue an incursion under the guise of restoring stability to eastern Ukraine.

“I call on Russia to step back from the brink. Step back from the border. Do not use peacekeeping as an excuse for war-making,” Rasmussen said.

While stopping short of committing to direct assistance in Ukraine’s ongoing conflict, Rasmussen said that NATO would intensify its cooperation with Ukraine on defense planning and reform.

Hours before Rasmussen’s arrival, clashes erupted in central Kiev as city authorities sought to clear away the remnants of a tent colony erected by demonstrators involved in the street uprising against pro-Russia President Viktor Yanukovych. At the time, protesters were angry about endemic corruption and wanted closer ties with the European Union.

In scenes reminiscent of that revolt, which climaxed with Yanukovych’s ouster in February, demonstrators set alight tires in their face-off against a volunteer battalion overseeing the clean-up operation.

In eastern Ukraine, government troops have made tentative progress in their strategy to retake Donetsk and other towns and cities. Armed forces have refrained from pitched urban battles, and instead favored pushing back their opponents with artillery fire. It has led to a growing number of civilians casualties.

Vishnevskiy Hospital, one of the city’s larger medical treatment facilities, is around 4 kilometers (less than 3 miles) from the main square. It has been used to provide treatment to civilian victims of the ongoing conflict.

“The hospital became a nightmare. This is absurd,” said 37-year old patient Dmitry Kozhur. “We came here to keep living, but now we are risking death.”

Kozhur said he now wants to join the 300,000 people that the mayor’s office says have already abandoned the once 1 million-person strong city.

As AP reporters were leaving the hospital, they heard the sound of four rounds of artillery being fired from a nearby neighborhood under rebel control. Although it wasn’t immediately possible to confirm the sequence of events, it appeared that the shells that hit the hospital may have been a response to rebel fire.

Neighbors of a house struck by rockets Wednesday said their homes were also near a position used by rebel artillery forces.

The Ukrainian military’s strategy has focused on driving a wedge between Donetsk and the other main stronghold of Luhansk. Efforts to seal off the border with Russia have been thwarted as border troops come under sustained and heavy rocket fire. Ukraine says a lot of those attacks have been carried out by Russian troops, which Moscow also fervently denies.

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Karmanau reported from Donetsk, Ukraine. Juergen Baetz contributed to this report from Brussels.

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