KIEV, Feb. 13 - Growing fears of a default pushed Ukraine's debt-insurance costs to four-year highs on Thursday increasing downward pressure on the country’s currency, the hryvnia.

"Ukraine is on the knife-edge of solvency risk," Reuters reported citing Gabriel Sterne, an economist at broker Exotix.

Concern has been growing over how Ukraine can prop up its currency and pay off its debt. Russia suspended a $15 billion bailout after Ukrainian President Viktor Yanukovych sacked his prime minister late last month.

The Ukrainian central bank brought in temporary currency controls last week after the hryvnia fell below 9 per dollar for the first time in five years. The bank said on Thursday controls may last longer than two weeks, as the currency continued to fall.

Investors were not convinced the central bank could continue to defend the hryvnia. The currency weakened further on Thursday, losing 1.5% against the dollar, and Ukraine's 5-year credit default swaps rose further, gaining 116 basis points from Wednesday's close to 1,241 bps, according to Markit.

Meanwhile, as anti-government protesters downed tools and marched on Kiev’s Independence Square on Thursday, an EU Commissioner said financial aid is available for Ukraine but only if it reforms.

The one-hour, nationwide strike was called by opposition leader and ex-boxing champion Vladimir Klitschko.

Both Klitschko and Yanukovych have met EU Enlargement Commissioner Stefan Fuele who has spent three days in Kiev.

“On the financial assistance, yes there are conditions, very transparent and I would call them reforms, reforms, reforms,” Fuele told a news conference in the capital.

“There is a need to take urgent steps on constitutional reforms, formation of the new inclusive government and ensuring free and fair elections.”

Calls for coalition government aside, Fuele has visited those injured in three months of pro-EU protests, both opposition casualties and wounded police officers. (rt/ez)