The killed Somali ministers include Qamar Aden Ali, the country's health minister, Ahmed Abdulahi Waayeel, the minister of education, and Ibrahim Hassan Addow, the minister of higher education.
Dubai-based Al Arabiya Television said one of its cameramen, Hasan al-Zubair, had been killed while Shabelle Media has already reported that its journalist Mohamed Amin Adan shabelle was killed in the event as well.
Islamists are fighting the UN-backed government, which controls small pockets of territory in the country.
Somalia's President Sheikh Sharif Sheikh Ahmad described the attack as a national disaster.