JOHANNESBURG (Reuters) - Artisanal miners torched a car belonging to miner Gemfields’ Mozambique operation on Saturday and attacked the occupants with pickaxes, injuring three employees and one security contractor, the company said.

Gemfields owns 75% of Montepuez Ruby Mining (MRM), which operates in northern Mozambique. The mine, considered to be the world’s largest deposit of rubies, is located in a region rife with crime, illegal mining and that is home to a nascent Islamist insurgency.

The attack follows an incident earlier in February when 800 artisanal miners invaded a pit belonging to MRM, 11 of whom died when parts of the pit collapsed.

“MRM has observed a dramatic and coordinated increase in the number of artisanal miners entering MRM’s concession, including women and children,” the company’s statement, sent to Reuters on Monday, said.

MRM says the artisanal miners are exploited by illegal ruby-smuggling syndicates, and receive only a fraction of the true market value of the rubies they obtain.

The latest attack seriously injured three MRM employees, while the security contractor sustained lighter injuries, MRM said.

Gemfields, which owns jewelry-maker Faberge, listed in London on Feb. 14.