At least 19 people have been killed in overnight clashes between rebels and government-backed militia in Yemen. The ambush occurred in Shabwa province, and is reportedly the third attack on government troops by militants in the area in five weeks. The fighting came a day after it was revealed that dozens of people have been killed recently in renewed violence in the area. The clashes have strained a truce agreed in February between Shia Houthi rebels and the government. At least 49 people have been killed in fighting between the rebels, known as Houthis, and the pro-government Ibn Aziz tribe, in recent days.