LIMA, Aug 31 (Reuters) - Peruvian miner Minsur has announced an investment of at least $2.25 billion as it expands its copper operations, the country's mining ministry said on Thursday.

The announcement followed a meeting between Minsur CEO Juan Luis Kruger and Peru's Energy and Mines Minister Oscar Vera.

Minsur is set to invest $1.8 billion in the Justa mine, which is owned by the firm and the Chilean mining company Copec . The deposit's reserves are expected to rise by 30%.

The mine produced 126,036 fine metric tons of copper last year and was the world's seventh-most productive copper mine, according to official data.

Peru is the world's No. 2 copper producer behind Chile.

Minsur also plans to invest some $450 million in the modernization of its polymetallic producer Minera Raura.

Minsur did not immediately respond to a request for comment. (Reporting by Marco Aquino; Editing by Brendan O'Boyle and Paul Simao)