Clashes in Somalia in late July killed more than two dozen people during fights with Islamic insurgents with al-Shabab and Somali government troops.
Al-Shabab declared its alliance with al-Qaida in February.
The African Union said in July it was sending in 4,000 troops to help government troops battle the insurgency.
Social activists who spoke to the U.N. humanitarian news agency IRIN on condition of anonymity said many of the traders in the country have either left or stopped importing food because of the difficulty of operating during the conflict.
Food prices, the activists said, have increased more than 30 percent. During Ramadan, IRIN said, the situation may become even worse as insurgents exploit the holy month to wage their campaign.
"The economic situation in which most residents find themselves is appalling," said one activist.