MOGADISHU, Dec 29 (Reuters) - Somali Prime Minister Ali Mohamad Gedi entered Mogadishu as hundreds of residents lined the streets on Friday, a day after Islamist rivals fled, witnesses said. The interim government's premier drove into the bullet-scarred capital in a 22-car convoy that included six "technicals" -- pick-up trucks mounted with heavy weaponry --, a Reuters witness travelling with Gedi said.