The first planeloads of US aid for the Russian wildfire tragedy arrived in Moscow on Saturday as firefighters battled to contain a fire still raging close to a top secret nuclear facility.
Officials said that nationwide the area ablaze was almost a quarter that of a week ago but there appeared to be little progress in reducing the size of the fire close to Russia's main nuclear research centre in Sarov.
Two US Air Force C-130 planes touched down at Vnukovo airport in the early hours of the morning, followed by a charter flight from California ordered by Governor Arnold Schwarzenegger, state television and the foreign ministry said.
"We will always remember this gesture, this arm that was extended to us at a very difficult time," the deputy head of the international department of the Russian emergencies ministry, Valery Shuikov, said at the airport.
Two additional C-130 flights were expected in the "next days", the Russian foreign ministry said in a statement. Another charter is also expected in the coming week.
According to the US State Department, the total value of the support from Russia's Cold War-era ex-foe is around 4.5 million dollars.
The delivery follows telephone talks between US President Barack Obama to his Russian counterpart Dmitry Medvedev.
The emergencies ministry said there were still 480 fires in Russia covering an area of 56,000 hectares (138,500 acres), a quarter of the area of almost 200,000 hectares (495,000 acres) reported at the peak of the crisis and down around 10,000 hectares (25,000 acres) from Friday.
"At the current moment the situation with the wildfires has improved considerably," said Emergencies Minister Sergei Shoigu in a statement on the ministry's website.
"The weather has not helped us. Everything has been done by the emergency services, the interior ministry, the defence ministry and volunteers."
Russia has sent thousands of firefighters to a nature reserve to battle a 1,000 hectare (2,500 acre) fire near the country's top nuclear research centre in Sarov, a town still closed to foreigners as in Soviet times.
The ground-level fire in the district of the village of Popovka, 17 kilometres (10 miles) southeast of Sarov, was unchanged in size from the day earlier, the local Mordovia region emergencies ministry said in a statement.
The Russian authorities said on August 4 that all radioactive materials had been removed from Sarov but some days later announced they had been returned as the danger had passed.
Along with Sarov, fires have also raged close to another research centre in the town of Snezhensk and the Mayak nuclear reprocessing site, both in the Urals, but the authorities appear to have controlled those fires.
"There are no threats from the forest fires to potentially dangerous sites. Potentially dangerous sites are reliably protected," said Shoigu.
But he also called for additional measures to be taken for warning of and putting out fires around strategically important and potentially dangerous sites in the future, adding that robotic systems would be installed.
The fires have been sparked by the worst heatwave in Russia's history, which destroyed one quarter of its crops and last week blanketed Moscow in a toxic smog that has raised major concern for public health.
There have also been fears the fires could stir up particles on land in western Russia still contaminated by the 1986 Chernobyl nuclear disaster but officials have said radiation is normal throughout the country.