Mr Yusuf's government has signed a three-month ceasefire
Two policemen have been killed in the Somali capital after their vehicle was blown up by a roadside bomb.
Three other people were injured in the attack which occurred a few minutes after a convoy carrying President Abdullahi Yusuf had driven past.
The attack followed fierce fighting in Mogadishu on Tuesday in which at least seven people were killed.
Last week, Mr Yusuf's government signed a ceasefire with an opposition bloc, but some Islamists rejected the deal.
Tuesday's fighting started when insurgents attacked government soldiers and Ethiopian troops who were searching for weapons in houses in the Hurwa and Karan districts of the capital.
Mogadishu has borne the brunt of the violence
Fourteen people were wounded in the fighting that continued until midnight.
Ethiopian troops have been in Somalia for 18 months since helping the government oust the Union of Islamic Courts (UIC) that ruled much of Somalia in 2006.
Earlier this week, the UN warned that the number of people in Somalia in need of emergency food aid is likely to rise to about 3.5 million in the coming months.
Mark Bowden, the UN's humanitarian co-ordinator for the region, said fighting between rival militias, successive droughts, sharply rising food prices and a collapse of the Somali currency were contributing to the crisis.
The country has experienced almost constant civil conflict since the collapse of Mohamed Siad Barre's regime in January 1991.
Last week's deal was signed by a top Islamist leader, Sheikh Sharif Sheikh Ahmed, and Prime Minister Nur Adde, but another Islamist leader has promised to continue fighting.
The three-month ceasefire provides for Ethiopian troops to leave the country within 120 days.