Open flames burning in Chernobyl’s exclusion zone have been extinguished after rain fell in the region north of Kyiv early on Tuesday morning, Ukraine’s emergency service has said, although activists monitoring the wildfires complained they had been barred from entering the area.

“There are no open flames,” the state emergency service said in a statement on Tuesday morning. There was still a “slight smouldering of the forest floor”, the agency added, noting that more than 400 firefighters and other personnel were still working in the area.

The eagerly awaited rain followed growing concerns that a series of grass fires in the 19-mile (30km) Chernobyl exclusion zone had reached the abandoned town of Pripyat and come within miles of the defunct nuclear reactor and a storage site for radioactive waste.

Yaroslav Yemelianenko, a tour operator who raised concerns about the fire on Monday, said he and his team had travelled to the area with humanitarian supplies for firefighters but were being held outside of the Chernobyl exclusion zone at a police checkpoint.

The rains had helped firefighters, he said, citing reports from inside the exclusion zone, although there were concerns that heavy winds could ignite new fires in the area.

The fire had sparked radiation fears, with concerns that clouds of radioactive smoke could be released and blow south towards Ukraine’s capital.

The Ukrainian government has called for calm. On Monday, the Ukrainian president, Volodymyr Zelenskiy, pledged to be transparent about the progress of the fires. “The public must know the truth and be safe,” he said.

Yemelianenko, who is also a member of public advisory board to the emergency service, posted a video on Monday showing flames and a cloud of smoke rising within sight of the protective shelter over the carcass of Chernobyl’s Unit 4 nuclear reactor, the site of the worst nuclear disaster in history.

Yemelianenko then wrote that the fire had reached the abandoned city of Pripyat and was just 2km (1.24 miles) away from the nuclear power plant and the Pidlisny radioactive waste disposal site.

“The situation is critical. The zone is burning,” he wrote in a Facebook post accompanied by a video of the blaze. Yemelianenko accused the government of covering up the severity of the fires.

Reuters also reported on Monday that Greenpeace believed the fire was considerably larger than official estimates.