"An erroneous strike by coalition warplanes killed six troops -- one officer and five soldiers," a military source based in the government stronghold Marib told AFP on condition of anonymity.

He said another 15 troops were wounded in the strike on a national army camp in the mountainous region of Nihm, a contested territory halfway between rebel-held Sanaa and Marib.

A second government military source gave a higher toll of 20 killed, including three prominent commanders.

The Saudi-led coalition did not immediately respond to requests for comment.

Saudi Arabia launched its Yemen military alliance in 2015 with the stated goal of restoring the government of President Abedrabbo Mansour Hadi to power and rolling back Huthi rebel gains.

In recent months, coalition-backed Yemeni troops have overrun multiple Huthi bases in Nihm -- held by the insurgents since 2014.

A bloody battleground, Nihm is a key gateway to the capital, which remains elusive with the military advance impeded by the treacherous mountain terrain and thousands of land mines planted by the Iran-backed rebels.