KATHMANDU (AFP) - Nepal ruled out the possibility Saturday of finding more survivors buried in the rubble from a massive earthquake that killed more than 6,700 people and devastated vast swathes of one of Asia's poorest countries.

One week on from Nepal's deadliest quake in over 80 years, hopes of detecting more signs of life among the ruins of the capital Kathmandu had all but disappeared and the focus was shifting to reaching survivors in far-flung areas who have yet to receive relief supplies.

The U.N. children's fund UNICEF warned of a race against time to avert an outbreak of disease among the 1.7 million youngsters estimated to be living in the worst-hit areas, with monsoon rains just a few weeks away.

The 7.8-magnitude quake wreaked a trail of death and destruction when it erupted around midday last Saturday, reducing much of Kathmandu to rubble and even triggering a deadly avalanche on Mount Everest.

"It has already been one week since the disaster," home ministry spokesman Laxmi Prasad Dhakal told AFP.

"We are trying our best in rescue and relief work but now I don't think that there is any possibility of survivors under the rubble."

As well as updating the death toll to 6,621, Dhakal put the number of injured at 14,023.

While multiple teams of rescuers from more than 20 countries have been using sniffer dogs and heat-seeking equipment to find survivors in the rubble, no one has been pulled alive since Thursday evening.

More than 100 people were also killed in neighboring India and China.