Sanaa, Jul 28 (IANS): Warplanes of the Saudi Arabia-led coalition mistakenly hit pro-government forces in Yemen's province of Lahj, killing 15 and wounding another 50, a media report said.

The air strikes hit fighters loyal to exiled Yemeni President Abd-Rabbo Mansour Hadi in Balah area in Lahj on Monday as they were advancing to besiege Shiite Houthi militia in the al-Anad airforce base, Xinhua reported, citing two military officials.

Houthi-controlled media reported airstrikes in the province of Saada, the group's stronghold that borders Saudi Arabia, as well.

The airstrikes occurred on the first day of a five-day humanitarian truce announced by the coalition to allow the delivery of aid to the people in need.

The Saudi-led coalition on Saturday announced a unilateral truce that came into effect at the request of Hadi.

The impoverished country has been rocked by four months of civil war between the Shiite Houthi group and Hadi's forces.

The coalition launched airstrikes on a daily basis since March 26 when Hadi fled to Riyadh to take refuge.

There is no sign that the warring parties intend to end the civil war, as the toll since late March has reached at least 1,693 civilians, according to UN agencies.