It was not immediately clear who carried out the attack, but al Shabaab militants linked to al Qaeda have claimed responsibility for a number of suicide bombs in Mogadishu this year.
“About seven well-armed men in government uniform entered the court today as soon as a car bomb exploded at the gate. We thought they were government soldiers,” said Aden Sabdow, who works at the mayor’s office adjacent to the court.
“There are many government officials inside the court which has been busy these days,” he said.
“Armed men entered the court and then we heard a blast. Then they started opening fire. We do not know the number of casualties,” said Hussein Ali, who works at the courts.
Four bodies in government uniform lay at the gate of the building, but it was not clear if they were government soldiers or attackers.
Somali forces arrived and besieged the court compound and there was a second blast while shots continued to ring out.
In control of much of the capital Mogadishu between 2009 and 2011, al Shabaab has been forced out of most major cities in central and southern Somalia by African Union peacekeepers.
But the hard-line Islamist group has hit back with a series of bomb attacks. In early April, a bomb went off outside the headquarters of Somalia’s biggest bank, Dahabshiil’s, wounding at least two people hours after al Shabaab ordered the company to cease operations in areas under its control.
Last month, al Shabaab claimed responsibility for suicide car bomb targeting a senior Somali security official which killed at least 10 people in central Mogadishu. The security official survived the attack, the city’s deadliest this year.