Emergency workers toiling to clean up an oil spill in the Black Sea have detected seven new slicks, a Russian official told the TASS state news agency on Friday, as authorities struggle to mitigate the effects of the nearly month-old disaster.

Fresh oil started pouring from a stricken Russian tanker in the Black Sea on Friday, said officials in Moscow, as Ukraine warned of "terrible environmental consequences" from the spill.By trying to "conceal the terrible environmental consequences" Moscow had left the entire Black Sea region vulnerable to the fallout,

The oil spill in the Black Sea that has hit Russian and Crimean coasts since mid-December is particularly hard to clean up because it involves a "heavy" fuel that is less likely to float.

Russian President Vladimir Putin said on Thursday that more needed to be done to clean up an oil spill in the Black Sea, saying efforts so far appeared to have been insufficient to deal with the ecological disaster.

Russian investigators have determined that an oil spill from two tankers in the Black Sea last month was smaller than initially thought, the Transport Ministry said on Thursday.