"A duty officer will remain on the job," the spokesman added, asking not to be named.
The German foreign ministry's website advised against all non-essential journeys to affected regions in Russia, especially for those with respiratory problems and for children.
Fires ravaging western Russia have already killed 52 people, while Moscow residents and tourists have been wheezing in the thickest smog to ever hit the capital since Russia's worst heatwave in decades broke out in July.
The Russian defence ministry ordered the evacuation of missiles from a depot outside Moscow as the authorities warned of the risk of fires reactivating contamination in an area hit by the 1986 Chernobyl nuclear disaster.
The capital's most famous landmarks, like the spires of the Kremlin towers or the onion domes of Orthodox churches, were largely invisible from a distance. Some flights at its Domodedovo international airport were being diverted.
"I woke up this morning, looked out of the window and saw a monstrous situation," declared President Dmitry Medvedev. "We all want this heatwave to pass but this is not in our hands, it is decided above."