Police are searching for a group of men who fatally injured a calf with rocks near the New South Wales-Queensland border last week.

The men were seen throwing rocks at the cow on the edge of the MacIntyre River at Little Bondi, near Boggabilla, on Thursday afternoon.

Police say the calf collapsed with extensive injuries and had to be euthanised.

The animal's attackers, who are described as being aged in their early 20s and of Aboriginal or Torres Strait Islander appearance, fled in a while Holden Commodore.

Witnesses have told police the offenders had been swimming in the river before the attack.