A pedestrian walks past the Central Bank headquarters in Moscow January 30, 2015. REUTERS/Grigory Dukor

KIEV (Reuters) - Ukraine’s central bank stepped up controls on banks’ access to foreign currency on Wednesday to try to stem the collapse of the hryvnia, preventing them from buying any for clients this week and limiting what they could buy for themselves.

The bank said in a statement that banks would not be able to buy foreign currency for clients “until 27 February 2015 inclusive” and that banks would only be allowed to buy foreign currency up to 0.5 percent of their regulatory capital.

Ukraine has scrambled to introduce restrictions on foreign currency purchases to try to stop a fall in the hryvnia, which has plunged about 13 percent over the last two days as an already fragile ceasefire in its east has all but unraveled.

Ukraine’s budget is stretched by fighting against pro-Russian rebels in two of its eastern regions and, with only $6.42 billion in its foreign exchange reserves, the central bank has few tools left to try to stop the currency’s collapse.

On Tuesday, the central bank tightened currency controls on importers and said earlier in the week that more measures would be taken to support the hryvnia, which has plunged 50 percent against the dollar this year. It also fell 50 percent against the dollar last year.