MOSCOW (AP) — Hundreds of Russian towns and cities are shrouded in heavy smoke from wildfires in Siberia and the Far East Thursday, and the blazes appear to be spreading in remote terrain.

Avialesookhrana, Russia's aerial forest protection service, said more than 30,000 square kilometers (11,850 square miles) are on fire, with the vast majority in areas that are hard to reach and where potential damage is likely to be less than the cost of fighting them.

Although the fires have not hit populated areas, heavy smoke from them is affecting about 800 communities, officials said, including the large cities of Novosibirsk, Krasnoyarsk and Chita.

Footage on Russian television showed planes dumping water on fires that were belching smoke amid vast stretches of trees. Firemen on the ground sprayed thin water streams on small fire remnants.

States of emergency have been declared in the regions of Irkutsk, Buryatia, Sakha and Krasnoyarsk.

In Chita, 4,700 kilometers (2,900 miles) east of Moscow, the center of the city was cloaked in heavy gray as Prime Minister Dmitry Medvedev visited. Medvedev called for effective use of local resources to fight the fires.

The Russian military has joined the firefighting efforts, sending transport planes and helicopters. But activists believe the government is not taking nearly enough action and plan to protest Thursday evening at the Ministry of Natural Resources.

Meteorologists say rain is expected in some of the burning areas, but not enough to put out the fires, state news agency Tass reported.

Some of the fires are believed to have been started by lightning strikes. Russia's Investigative Committee, the country's main criminal investigative body, said Thursday it was sending representatives to the region to probe the causes.