Heavy shellfire rocked the capital, Bissau, after a brief lull as government forces and their Senegalese and Guinean allies fought to flush rebels out of their strongholds in the city. But the task was proving difficult, with insurgents still controlling parts of the sprawling Bra military garrison and access to the airport and with loyalist forces having to pick their way forward through rebel minefields. "Shells have violently resumed," one French diplomat said by satellite telephone from Bissau. "I don't know to what direction shells are going because we are keeping indoors." "Our objective is the airport. We will continue until we control it," a Senegalese official said.