Troops from Somalia's National Intelligence and Security Agency [NISA] were reported to have carried out a massive security operation in Kahda district, south of Mogadishu.
The operation came as the security situation in the area deteriorated in the past few days after Al Shabaab launched assassinations and attacks against the security personnel.
The NISA officers detained several people in connection with the rising killings of both civilians and security forces in the district, which is vulnerable to the militant raids.
On Sunday night, Al Shabaab fighters attacked security forces on a security patrol in Kahda area, killing at least one soldier dead, and wounding several others, according to the locals.
There has been an upsurge of violence in the seaside city of three million people which government officials blame on the Al Qaeda-linked Al Shabaab militants.