This combination of satellite pictures shows an aerial view of Marj before flash floods on August 6 and after flash flooding on September 11. AFP

Libyan authorities blocked civilians from entering the flood-stricken eastern city of Derna on Friday so search teams could look through the mud and wrecked buildings for 10,100 people still missing after the known toll rose to 11,300 dead. Meanwhile, images taken by satellite show the physical devastation from a flood that killed at least 11,300 people in the eastern Libyan city of Derna. Two dams above Derna burst early Monday under the pressure from rain dropped by a storm.

The pent-up water swept blocks of low-lying downtown Derna out to the Mediterranean Sea. Many said they heard loud explosions as the dams exploded. A flood several metres (many feet) high rolled down a mountainside into the city. Images made about 400 miles above the earth’s surface show that the storm left a brown layer of mud and dirt across the city.

The disaster after two dams collapsed in heavy rains and sent a massive flood gushing into the Mediterranean city early on Monday underscored the storm's intensity but also Libya's vulnerability. The oil-rich state since 2014 has been split between rival governments in the east and west backed by various militia forces and international patrons. Derna was being evacuated and only search and rescue teams would be allowed to enter, Salam al-Fergany, director general of the Ambulance and Emergency Service in eastern Libya, announced late on Thursday.

The disaster has brought rare unity, as government agencies across Libya's divide rushed to help the affected areas, with the first aid convoys arriving in Derna on Tuesday evening. Relief efforts have been slowed by the destruction after several bridges that connect the city were destroyed. The Libyan Red Crescent said as of Thursday that 11,300 people in Derna had died and another 10,100 were reported missing.

Mediterranean storm Daniel also killed about 170 people elsewhere in the country. Eastern Libya’s health minister, Othman Abduljaleel, has said the burials so far were in mass graves outside Derna and nearby towns and cities. Abduljaleel said rescue teams were searching wrecked buildings in the city centre and divers were combing the sea off Derna. Soon after the storm hit the city on Sunday night, residents said they heard loud explosions when the dams outside the city collapsed.

Floodwaters gushed down Wadi Derna, a valley that cuts through the city, crashing through buildings and washing people out to sea. Lori Hieber Girardet, the head of the risk knowledge branch the UN Office for Disaster Risk Reduction, told The Associated Press on Thursday that because of years of chaos and conflict Libyan "government institutions are not functioning as they should.”

As a result, she said, "The amount of attention that should be paid to disaster management, to disaster risk management isn’t adequate.” The satellite pictures show dirt and debris stretching out to sea into Derna’s shallow waters, which appeared visibly brown near the shoreline. Many bodies washed out to sea have come back with the tide, rescue workers say.

The floods have displaced at least 30,000 people in Derna, according to the UN's International Organization for Migration, and several thousand others were forced to leave their homes in other eastern towns, it said. Bridges and other basic infrastructure have also been wiped out, especially buildings near the Wadi Derna river. Because of the damage to roads, aid only began trickling into the city on Tuesday evening.

Associated Press