(Reuters) -A senior Ukrainian intelligence official said on Thursday that armed groups he described as Russians opposed to the Kremlin were pressing an incursion into Russian territory and had turned two border regions into "active combat zones".
But the governor of one of the Russian regions hit by the attacks said, after a visit to villages in an area, that hostile troops were no longer there.
Three Ukraine-based groups issued statements saying they were pursuing armed operations in Belgorod and Kursk regions and asking residents to evacuate localities for their own safety.
"Kursk and Belgorod regions are now an area of active combat actions. This is what we confirm," Andriy Yusov, a spokesperson for the GUR intelligence directorate, told national television.
"And as stated by the volunteers and rebels, we are talking about Russian citizens who, having no other options, are defending their civil right with arms against the Putin regime."
Vyachslav Gladkov, governor of Russia's Belgorod region, said in an account posted on Telegram that there were no Ukrainian forces in one of the areas that had come under attack.
"I can state that there are no Ukrainian troops on the territory of the region," he wrote in the account posted after midnight local time. "The fighting is taking place outside it."
But Gladkov said the village of Kozinka "was badly hit. The damage is very serious." Residents had been evacuated to places where they were now safe.
Gladkov earlier said that two people were killed and at least 20 injured in attacks by Ukrainian armed forces.
Russian military bloggers had earlier reported that Russian paratroops had been dispatched to Kozinka. Russia's Defence Ministry said it had foiled an attack by the Ukrainian army.
Kursk regional governor, Roman Starovoit, gave few details, but noted on Telegram that "Ukrainian terrorists have not stopped their attempts to bring saboteurs into our territory".
One of the three armed groups, the Freedom of Russia Legion, said on Telegram that in view of the "limited military operation" being conducted in the two regions, it was asking residents of certain towns to leave the area.
' A second, the Siberian Battalion, said it had observed "a mood of panic in the town of Grayvoron -- next to Kozinka - with cars queuing to leave.
Two of the groups had reported launching a cross-border incursion earlier this week.
In the past, Russian officials have cast the groups as puppets of the Ukrainian military and U.S. Central Intelligence Agency, which Moscow says is trying to foment chaos in Russia.
The Freedom of Russia legion and the Russian Volunteer Corps have previously claimed responsibility for other cross-border raids into Russia from Ukraine.