MOGADISHU, March 20 (Reuters) - Two U.N. staff escaped unharmed when a roadside bomb hit their convoy en route to Mogadishu on Tuesday, but it was unclear whether the attack was targeted against the world body, a U.N. spokeswoman said. "The U.N. staff were unharmed and the convoy proceeded to Mogadishu," U.N. spokeswoman Sandra Macharia said by telephone from Nairobi. "We cannot say if it was a direct attack on us." Three policemen guarding the convoy were wounded in the attack which took place some 30km (18.6 miles) outside the Somali capital, she said. African Union (AU) peacekeepers began landing in Somalia this month to help the interim government tackle insecurity in the Horn of Africa country, deprived of central rule since warlords toppled dictator Mohamed Siad Barre in 1991. Lawlessness is particularly bad in Mogadishu with almost daily insurgent attacks against the government and its allies.