TOKYO (Reuters) - Tokyo Electric Power Co, the operator of the crippled Fukushima nuclear plant, said on Wednesday that it cannot confirm the exact volume of contaminated groundwater that is leaking into the ocean.

The Japanese government believes radiation-contaminated water has been leaking into the Pacific Ocean at a rate of 300 tons a day, an industry ministry official told reporters on Wednesday.

"We are not currently able to say clearly how much groundwater is actually flowing into the ocean," said Tokyo Electric Power spokesman Noriyuki Imaizumi in response to a reporter's question about the government estimate.

(Reporting by Mari Saito and Antoni Slodkowski; Editing by Edmund Klamann)