Standard & Poor's ratings agency today lowered Ukraine's long-term rating from 'CCC+' to 'CCC'.

The agency said the political crisis has put the government's ability to service its debt at risk and raised uncertainty over Russia providing promised aid.

"The downgrade reflects our view that the political situation in Ukraine has deteriorated substantially," the agency said in a note a day after the deadliest day in the country's three month old political crisis.

"We believe that this raises uncertainty regarding the continued provision of Russian financial support over the course of 2014, and puts the government's capability to meet debt service at increasing risk," it said.

The crisis in economically-struggling Ukraine erupted in November when President Viktor Yanukovych decided unexpectedly to reject a European Union integration deal years in the making in favour of closer ties with Russia.

Moscow then promised to provide a $15 billion bailout to its former satellite and to slash prices that Kiev paid for energy supplies.

The Kremlin provided the first $3 billion tranche of the promised aid at the end of January and had promised to release the second tranche this week.

The country's Health Ministry said that 77 people have died since Tuesday, including several police officers.