Protesters demanded Ukraine's interior minister resign on Thursday after an opposition journalist known for documenting the extravagance of the country's political elite was chased down in her car and savagely beaten in a midnight attack.

Clutching pictures of Tetyana Chornovil's badly bruised face, hundreds marched on the Interior Ministry in the capital, Kyiv.

The attack on the 34-year-old restored passion to protests which have been losing steam more than a month after the government spurned a pact on closer ties with the European Union, turning instead to former Soviet master Moscow.

Pro-EU demonstrators have been occupying central Kyiv but their numbers have been falling since Russia offered Ukraine a $15-billion bailout this month.

Interior Minister Vitaly Zakharchenko had already become a target of opposition anger following a violent crackdown on protesters by police late last month that helped swell the demonstrations.

Attacks followed online photo post

The attack on Chornovil, shortly after midnight on Wednesday, came hours after she posted pictures online of what she said was Zakharchenko's home, part of a campaign to expose the opulence of the political elite under President Viktor Yanukovich.

"Our police no longer protect their people, but fight them instead, hurt and oppress them," said protester Valentina Gorilova, a 47-year-old housewife.

Some protesters, their hands chained, kneeled before a row of police in mock supplication.

With Ukraine winding down for the Orthodox Christian holiday season, the opposition movement has shown signs of waning. A hard core of hundreds continue to camp out around braziers on Kyiv's Independence Square, swelled by weekly mass rallies of around 100,000 or more.

Chornovil, who has played an active role in the protests, shot to prominence last year when she infiltrated the grounds of Yanukovich's opulent residence in a park near the Dnieper River.

She has since posted photographs online of the homes of other senior officials. Zakharchenko was her target on Tuesday. "Here lives the executioner," the journalist wrote in her blog, above pictures of a handsome country property.

Hours later, Chornovil was chased on a road outside the capital, a dashboard camera capturing how a black Porsche Cayenne veered and rammed into her car before at least two men jumped out. Photographs and video released later showed a beaten and bloodied Chornovil on a hospital bed. Her lips were swollen and split, one eye blackened and closed by bruising.

The Organization for Security and Co-operation in Europe (OSCE) and the United States embassy in Kyiv condemned the attack.

The embassy noted "a strikingly similar series of events over the last few weeks, targeting individuals, property, and political activity, apparently aimed at intimidating or punishing those linked to the ... protests."

Media reports said another opposition activist was stabbed in the eastern city of Kharkiv on Tuesday.

Yanukuvich on Wednesday called on police to find those responsible for the attack on Chornovil. Two men were later detained and police said they had identified a third.

Billions in Russian aid

The president's pivot away from Europe last month has thrown the country of 46 million people into turmoil, exposing a deep rift among Ukrainians over whether their future lies with the EU or Russia.

Rejecting the EU trade deal, Yanukuvich turned instead to Russia for an aid package worth $15 billion to help ease a worsening financial crisis. It received a first $3-billion tranche this week.

On Thursday, ratings agency Standard and Poor's revised the outlook on Ukraine's long-term sovereign 'B-' rating to stable from negative, saying the bailout would cover the country's financing needs over the next year.