(adds deaths in southern fighting) SANAA, June 21 (Reuters) - Arab air strikes killed 15 people and wounded dozens across Yemen late on Saturday, the Houthi-run Saba news agency reported. A Saudi-led Arab coalition has been bombarding Houthi rebels and allied army units since March 26 in a campaign to restore exiled President Abd-Rabbu Mansour Hadi to power. Hadi, Riyadh's ally, was pushed aside last year when Houthis advancing from their **rthern strongholds overran the government in the capital Sanaa and went on to capture lands to the south.