(Adds details, background) NAIROBI, April 1 (Reuters) - A Ugandan soldier was killed by artillery in Mogadishu in the first death reported by African peacekeepers in the Somali capital, a spokesman said on Sunday. The coastal city is suffering its worst fighting for years as government troops backed by Ethiopian tanks and helicopter gunships seek to crush Islamist rebels and clan militia. A fourth day of battles began on Sunday. "Our troops were guarding the presidential compound on Saturday when it was struck by mortars. One of our soldiers was killed," Uganda's military spokesman Major Felix Kulayigye told Reuters by telephone from Kampala. About 1,200 Ugandan troops formed the vanguard of a proposed 8,000-strong African Union force aimed at helping the government assert authority in the Horn of Africa country. Previously, Uganda said only two of its soldiers had been lightly wounded in an insurgent ambush. Somalia descended into chaos after dictator Mohamed Siad Barre was overthrown in 1991.
