It was one in a series of assassination attempts against prominent figures in Somalia.
Abdullahi Ahmad Afrah, the country's minister for trade, said he survived an assassination attempt in Mogadishu on Tuesday night when a roadside bomb hit his body guards' car, killing one of them and injuring three others, one of them seriously.
Afrah, who was riding in another car, said: "It was an assassination attempt. But it failed. Even the targeted car was lightly damaged."
At Mogadishu's Bakara market, police officer Abdi Mohamed Shino, who was in the lorry targeted by the grenades, said police opened fire after the attack and injured two civilians.
"Two civilians died in the [grenade] blast and two others, including a policeman, [were] wounded," Shino said. "I think the attackers disappeared into the market."
Abdisalan Mukhtar, who sells water at the market, said three men armed with assault rifles and two pistols arrived and hurled three hand grenades at the police.
"Then police opened fire and I saw two dead bodies lying on the ground."