“Two men armed with pistols shot him dead, he instantly died and the assailants escaped the scene,” said Mohamud Hurshe, who worked with Abukar Hassan Kadaf, the head of the Somaliweyn station.
It was the second killing of a journalist in Mogadishu this year.
Hurshe said his colleague was killed as he walked home in the Wadajir district in the south of the Somali capital.
“We don’t know the reason,” Hurshe said.
Police officer Mohamed Abdulkadir said the shooting was under investigation but initial reports show there were two attackers.
Radio Somaliweyn is an independent station operating in the north of Mogadishu. It was attacked in 2010 by Islamist Shebab rebels who took a transmitter and a computer.
At the end of January, the director of another Somali radio station was killed while returning to his home.
Press freedom watchdog Reporters Without Borders has described Somalia as the deadliest African nation for journalists.
Somalia has had no effective government since 1991 and in recent years the Shebab rebels and other groups have taken an increasing hold on large parts of the country.
Osama bin Laden’s successor Ayman al-Zawahiri announced last week that Shebab fighters had joined forces with Al-Qaeda.