KIEV, Ukraine -- Ukrainian troops have recaptured more than a dozen eastern villages from pro-Russia separatists but Russia is allowing the rebels to attack Ukrainian border posts from its territory, a top security official said Friday.
National Security Council Secretary Andriy Parubiy also said Russia was massing troops near the Ukrainian border -- a statement that could not immediately be verified. The two neighbors share a 2,000-kilometer (1,250-mile) long border that is unmarked and unguarded outside of a few checkpoints.
There was no immediate response from Russia to either statement, which came as President Petro Poroshenko expressed a willingness to take part in new peace talks as early as Saturday.
Ukraine says Russia is arming and supporting the separatists in the east, a charge that Russia denies. Ukraine is wary about Russia possibly grabbing more territory after President Vladimir Putin annexed Crimea in March. The rebels have asked to join Russia and Russian nationalists have urged Putin to send troops into Ukraine, but Putin has resisted those demands for fear of more Western sanctions.
Poroshenko, in a statement Friday, said Ukraine had proposed a place and a time for talks but had not heard back from the other parties. Representatives from Ukraine, Russia and the rebels took part in earlier talks along with representatives of the Organization for Security and Cooperation in Europe.
Parubiy said government forces were attacking rebel positions in eastern Ukraine with artillery and planes and that 17 villages had been recaptured since a unilateral cease fire expired Monday.
He said Ukrainian forces now control 23 of the 36 local regions within Donetsk and Luhansk provinces, the two regions along the Russian border that have declared independence from Poroshenko's government in Kiev. They are not in control, however, of the region's two main cities.
Ukrainian border checkpoints in the Luhansk and Donetsk regions were still being attacked, both from inside Ukraine and from Russian territory, he said. One of the reasons the cease-fire was not extended this week is that the rebels had not handed back three border posts as Poroshenko had demanded.
"Fighting aiming at defending the border and liquidating (rebels) in the Luhansk and Donetsk regions continues," Parubiy told journalists at a news conference in Kiev. "This is taking place during the constant movement of military equipment and armed forces of the Russian Federation close to the Ukraine's border."
Claims from either side in the conflict are difficult to verify.
Insurgents in the Luhansk province said Friday that they have killed 125 Ukrainian troops, destroyed nine armored vehicles and downed three combat aircraft since Wednesday.
Rebels shelled the Donetsk airport overnight and an AP reporter at the site said a radar or communications tower there was still burning Friday.
Balint Szlanko contributed from Donetsk, Ukraine.