Yemen's capital has been rocked by a night of deafening explosions and gunfire as troops loyal to the president, Ali Abdullah Saleh, battled with rebel tribesmen and defected soldiers for control of the city.
The violence was some of the fiercest in months and has prompted fears that the fate of the country's nine-month civilian uprising may be sliding into the hands of Yemen's fractious armed forces.
The fighting broke out around 11pm on Sunday with sporadic bursts of gunfire. By dawn a series of huge explosions had ripped through buildings in the north, echoing around the surrounding mountains.
Three teenage protesters were severely wounded when a hail of rockets thudded into Change Square – the tented shantytown in central Sana'a where thousands of demonstrators have been camped out since February calling for Saleh's resignation. It is the fourth time in the past month that shells have fallen on the camp.
"Their wounds are appalling," said Anas Noman, a third-year medical student volunteering in the camp's mosque, now a field hospital. "We've transferred one of them to a nearby hospital for an amputation of his leg."