ADEN: Saudi-led coalition warplanes Monday hit positions of pro-government forces in south Yemen by mistake, killing 12 people on the first day of a humanitarian truce, Yemeni military sources said.

The raids targeted positions in Lahej province, where Saudi-supported loyalists have been tightening the noose on Iran-backed Shiite Houthi rebels, the sources said.

At least 30 others were wounded in the raids on hills overlooking the rebel-held Al-Anad airbase, as well as in nearby Radfan, the sources said.

Witnesses and sources in the pro-government Popular Resistance militia confirmed the raids.

The Riyadh-based leadership of the coalition was not reachable for a comment.

The airstrikes came hours after the beginning of a five-day truce declared by the coalition to allow desperately needed aid deliveries. 

In announcing the truce, the coalition had reserved the right to respond to military activity or movement by the rebels and their allies.