The attack on the base in Laanta Buuro, about 45 km from the capital, came shortly after African Union troops from Kenya said they had killed 34 al Shabaab militants in two separate incidents on Saturday and Sunday.
The Somali government is battling to rebuild the nation after more than two decades of conflict.
Al Shabaab, which aims to topple the Western-backed government, ruled large parts of Somalia until 2011 when the African Union and Somali troops drove it out of Mogadishu.
However, military officer Abdullahi told Reuters on Monday that “the militants were so many, and well armed.
“The soldiers fled the base, only one soldier died, but the militants took nine vehicles.”
Sheikh Abdiasis Musab, al Shabaab’s military spokesperson confirmed the attack, saying that it had killed 70 men.
“We left only one truck that was burning. Seven of the vehicles we took had anti-aircraft guns fixed on,” he said.
The militants often inflate casualty numbers and downplay the number of their own fighters killed.