Prisoners escape in northern NSW

Three men have escaped from prison after threatening an officer with knives, a hammer and a screwdriver in northern NSW.

Police say Andrew Fernando, Greg Walford and Dean Boney - aged between 20 and 22 and wearing prison greens - stole a four-wheel drive from the minimum-security Brewarrina Correctional Centre before leading officers on two chases early on Saturday.

People should not approach the men, who are serving time for aggravated break and enter, but have been asked to call triple-zero.