At least 185 people have been killed in avalanches that blocked a mountain pass north of the Afghan capital, according to official sources.

Rescue teams kept digging through mounds of snow on Thursday searching for victims as the hope of finding more survivors faded.

Suhrab Ali Safari, the public works minister, said five more bodies were discovered on Thursday on the pass, 115km north of Kabul, bringing the total to 171. It was unclear how many more bodies may be buried in the snow.

Hundreds of soldiers and police plowed through huge snowdrifts to clear the 3.5km of road that had been blocked off when a series of avalanches  sent tons of snow and ice crashing down onto hundreds of vehicles along a treacherous stretch of highway on Monday.

A big search-and-rescue operation using US helicopters has rescued over 2,500 people but many more are feared still trapped in their cars.

General Mohammad Rajab, head of the Kabul-Salang highway, said rescue workers were still searching for survivors.

"The rescue operation is still ongoing, and the death toll may rise as we dig out dozens of other frozen bodies," he said.

Tunnel blocked

Days of heavy snowfall triggered the snow slides, which blocked the 2.6km Salang tunnel - a historic engineering feat that links Kabul and Afghanistan's north.

More than 200 lorries, buses and cars were trapped inside the tunnel at 3,400 metres above sea level.

Hamid Karzai, the Afghan president, said he was saddened by the deaths and ordered government workers to do all possible to open the pass.

Mohammad Hanif Atmar, the interior minister, fended off questions about why the road was open in the first place, insisting the situation appeared manageable until the storm struck abruptly.

"All of a sudden, a storm hit the area which resulted in a number of avalanches hitting the main highway and closing the road for up to 3.5km," he said.

Heavy snowfall and rain also caused floods in the south of the country. Zalmay Ayoubi, the spokesman for the governor of southern Kandahar province, said six people had been killed and 10 were missing as a result of floods.