"We have a very complicated situation because as a whole in the country around a quarter of the grain crops have been burned," Russian news agencies quoted the president as saying in the southern town of Taganrog.
Medvedev also said that though he had lifted the state of emergency in Vladimir, Voronezh and Marii El regions, the situation remained "complicated" in another four regions - Mordovia, Moscow, Nizhny Novgorod and Ryazan.
Russia is battling what experts say is the worst heatwave in its history, which has affected nearly all areas of life and may cost it one per cent of gross domestic product, $15bn.
Opposition groups and activists attempted to hold a rally in Moscow against what they saw as the government's slow response to the fires and the acrid smoke that has engulfed the capital in recent weeks.
On Thursday, police detained 35 people near the office of mayor Yuri Luzhkov, who has come under pressure for being slow to return to the Russian capital last week after it was engulfed by smoke from wildfires outside the city.
Among those arrested was prominent rights activist Lev Ponomaryov, who said the city government "has long since discredited itself".