At least 800 unexploded artillery shells from World War II were found by maintenance workers in northwestern Moscow on Wednesday, an Emergency Situations Ministry spokesman said.
He said about 100 residents had been evacuated from nearby apartment buildings and the area was closed to traffic.
Bomb disposal experts are currently working at the site, reportedly a World War II ordnance depot.
According to some media reports, as many as 2,000 shells could be located in the former underground storage facility.
The shells were discovered during utilities maintenance work, including the replacement of underground water pipes.
City authorities earlier said that between 200 and 300 unexploded aviation bombs, artillery shells and other ammunition is found in Moscow each year, mostly in northern and northwestern parts of the city.
MOSCOW, March 17 (RIA Novosti)