Gunmen hijacked four ship within 48 hours last week. Cash retrieved from ransoms is paying for weapons and salaries of fighters on both sides of Somalia's conflict.
Failed talks and the killing of yet another aid worker highlight the growing humanitarian crisis in the Horn of Africa.
The attack undermines a UN-mediated cease-fire signed last week between the government and opposition groups as the country's humanitarian crisis worsens.
Monday, the government and an opposition bloc signed a UN-brokered peace deal. But Tuesday, Islamist hard-liners said they would continue to fight.
Mogadishu's recent outbreak of violence appeared linked to a May airstrike that killed Hashi Aden Ayro, a Somali Islamist leader who the US says has links to Al Qaeda.
News of an airstrike on Aden Hashi Ayro came on the heels of the State Department's annual report on terrorism, which concluded that Al Qaeda was rebuilding in Pakistan.
Latest missile strike at the East Africa nation, aimed at a suspected Al Qaeda operative, keeps terrorists off balance. But some say US should do more to nation-build in Somalia.