The reporter said buildings around the area were severely damaged by the explosion, and several destroyed cars on the road were burning. A truck loaded with explosives went off at the entrance of a hotel, according to security sources.
"This was very terrible, the bomb went off alongside the busy road and left many people dead".
There were no immediate claims of responsibility, although the Islamist Al Shabaab group has carried out regular attacks in the country.
"This was very disgusting", witness Ismail Yusuf told AFP news agency.
Emergency services were overwhelmed as they sought to respond to the bombing.
Later on Saturday, a second blast took place in the city's Madina district.
"This was very frightful incident".
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"The scene turned deadly very immediately" Ali Abdullahi, a witnesses said, "This is the largest explosion I ever heard".
"They have collected tens of dead and injured and the work is still ongoing", he said.
The Safari Hotel is close to Somalia's foreign ministry.
CBC News reported that the attack targeted a hotel on the central street.
In any case, the devastation caused was widespread. "We are still busy transporting casualties", he said, adding that there were bodies under the rubble.
However, the militants continue to control rural areas and launch attacks on military, government and civilian targets in Somalia, as well as terrorist raids in neighbouring Kenya.
The blast, which also wounded at least 15 people, occurred two days after the head of the U.S. Africa Command was in town to meet with Somalia's president.