Zakia Hussein Ahmed, deputy police commander, said the explosive materials, which also included grenades, cartridges and other substances used for bomb-making were discovered in an underground site in an operation in the vicinity of Elasha Biyaha, outskirts of Mogadishu.
"The weapons we discovered include explosive vests, bombs, and landmines, heavy and light weapons," Ahmed told journalists in Mogadishu on Sunday.
She also noted that Somali national army apprehended 49 al-Shabab suspects in two different operations in Lower Shabelle region in southern Somalia.
Ahmed said security forces were acting on a tip-off from residents, which led to the latest operations.
This move comes while Mogadishu is on high alert as police forces blocked the main roads of the capital to ward off possible attacks by militants.
Somali national forces, backed by African Union Mission in Somalia, drove out al-Shabab militants from the capital in August 2011, but the militants are still capable of conducting attacks on government installations, hotels, restaurants and other public places.