African Barrick Gold, a division of Toronto-based Barrick Gold, said Tuesday seven intruders were killed and a dozen more were injured Monday at its North Mara mine in Tanzania.

The company said 800 "criminal intruders" were trying to steal ore from the mine when police were called. It says the thieves attacked the police with machetes, rocks and hammers.

African Barrick said the police have increased their presence in the area and are investigating. The company has also started its own  review.

"Although full details are yet to be confirmed, African Barrick Gold sincerely regrets any loss of life or injury on or near its mine sites," the company said in a statement.

"The company will continue to support the government and the community in their efforts to improve law and order and security in the North Mara region."

The company said the incident had no material impact on operations.

Produced about 213,000 ounces in 2010 

The company said 1,753 people worked at the mine at the end of last year including 829 African Barrick employees and 924 contractors.

North Mara produced about 213,000 ounces of gold in 2010.

Bullion reached an all time high of $1,575.79 US an ounce on May 2 after gaining 30 per cent in 2010. June gold was closed Tuesday on the New York Mercantile Exchange at $1,480.00 US, down $10.60.

The mine is situated in the Tarime district of Mara region in northwest Tanzania, approximately 100 kilometres east of Lake Victoria and 20 kilometres south of the Kenyan border.

Barrick Gold, the world's largest gold miner, holds a roughly 74 per cent stake in African Barrick, which owns the company's former mines in Tanzania.

Shares in African Barrick, which trade in London, closed down 5.75 per cent at 4.69 pounds Tuesday.

With files from The Canadian Press