Witnesses in Somalia's capital say at least two people have been killed by a roadside bomb explosion.

The blast Sunday in Mogadishu's Waberi district targeted a vehicle carrying Somali government soldiers.

Witnesses say the explosion missed the troops but killed two civilians who were standing nearby.  There was no immediate claim of responsibility.

On Saturday in Mogadishu, at least 10 people were killed in an artillery battle between hardline Islamist insurgents and government forces.

The battle began when insurgents fired on Mogadishu's airport and the Somali presidential palace as President Sheikh Sharif Sheikh Ahmed returned from Kenya.

Most of the casualties occurred in Mogadishu's sprawling Bakara market.  At least 17 people were wounded.

In Kenya, President Sharif met Thursday with U.S. Secretary of State Hillary Clinton, who promised to increase U.S. assistance to his government.

The United States has expressed concern Somalia could become a haven for terrorists if Islamist militant groups, led by al-Shabab, seize control of the country.

The groups already control much of southern Somalia and parts of the capital.

U.S. officials acknowledged in June that they had supplied weapons to President Sharif's government.  The president told reporters on Thursday that Secretary Clinton had pledged more help with security and humanitarian aid.

Some information for this report was provided by AFP.