A newly-released video has captured the moment a rancher's son was tasered by federal agents and the use of force has today provoked fresh outrage among libertarian groups across the country.

Ammon Bundy, the son of the Nevada rancher locked in an increasingly tense land dispute with the federal government, is shown being shot with a taser and threatened by police dogs.

The confrontation took place Wednesday and was caught on video by Bundy supporters and relatives who got into an aggressive- and at times violent- face off with the officers.