MOGADISHU, Jan 19 (Reuters) - More than a dozen mortar explosions rocked Mogadishu and gunfire rattled out on Friday night in the latest outbreak of violence in chaotic Somalia. "I have heard 14 mortars falling and exploding, and now there is gunfire," said Reuters reporter Sahal Abdulle. Ethiopian troops who helped the Somali interim government drive Islamists out of Mogadishu over the New Year have in past days been the target of attacks from unknown groups.