A loud blast rocked the bullet-scarred capital, shaking the homes of residents, killing at least three people and injuring nine, Somali news agency Shabelle reported.
"Soon after we said our Friday prayers a huge explosion happened and the earth beneath our feet shook," said Ahmed Omar, a resident who lives near the blast site.
Unknown assailants flung grenades at road junctions in the seaside capital as well, killing at least one person.
Meanwhile, some five moviegoers in Baidoa were killed Thursday night when a grenade was thrown at the theatre they were in, the BBC said.
The motive of the attack was not immediately clear but the cinema house is known to show films with nudity in it.
Much of Somalia was ruled by a hard-line Islamist group for the last half of 2006, which often broke up movie viewings of Western and Indian films, saying they were immoral.
Baidoa was one of the few towns controlled by the transitional government during that time.
Ethiopian-backed government troops ousted the Islamists over the New Year in a US-blessed assault that sparked an Iraq-style insurgency from remnants of the radical group, which is said to have ties to the al-Qaeda terror network.
In the Kenyan capital Nairobi, US Ambassador to Kenya Michael Ranneberger presided over a ceremony that signed away 4 million dollars in development aid to the Somali government, which is struggling to cement its authority in the volatile country.
In a statement, the embassy said 1.25 million dollars would go toward a national reconciliation conference - set to be held in April but postponed again until next month - which is seen as the only way to bring stability to the anarchic nation of 10 million people.
Somalia was plunged into lawlessness in 1991 after warlords toppled dictator Mohammed Siad Barre and then turned on each other. dpa tg pmc
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