KIEV (AFP) - Russia's annexation of the Crimea peninsula could cost Kiev hundreds of billions of dollars, Ukraine's interim prime minister Arseniy Yatsenyuk said on Friday, quoted by Interfax news agency.

Speaking to reporters in Kiev after signing a deal in Brussels on closer ties with the EU, Yatsenyuk said Russia was seizing "dozens of installations" from Ukraine worth "not billions, but hundreds of billions of dollars".

"Russia can only wait patiently: in the near future the state of Ukraine will be filing complaints before international courts," he said.

Moscow officially claimed Crimea as its territory on Friday after pro-Russian forces took control of the peninsula last month, in a move Ukraine and the West have denounced as illegal.

Russian-backed leaders in Crimea moved Monday to nationalise assets of Chornomornaftogaz, a unit of Ukraine's state-owned Naftogaz, in a decision that also included the "continental shelf and exclusive economic zone" in the Black Sea.