Kyiv says sporadic fighting has occurred between Ukrainian forces and pro-Russian separatists in eastern Ukraine despite a cease-fire agreement.
Ukraine's National Security and Defense Council said on September 24 that eight soldiers were wounded over the past 24 hours.
Council spokesman Andriy Lysenko said rebels kept provoking government troops into returning fire.
A residential building in the rebel-held city of Donetsk was reportedly damaged by shelling. Rebels were quoted as saying two people were killed in the attack. The claim could not be independently confirmed.
The cease-fire has been in force since September 5 and appears to be largely holding, despite repeated violations.
A second agreement to establish a 30-kilometer-wide buffer zone along the front line took effect on September 20.
NATO spokesman Jay Janzen said on September 24 that the alliance has observed a significant withdrawal of Russian forces from inside Ukraine but that many Russian troops remain stationed near the border.
WATCH: Levko Stek of RFE/RL's Ukrainian Service filmed these exchanges of fire near the city of Debaltseve on September 21 and 22:
Janzen said in an e-mailed message to Reuters, "There has been a significant pullback of Russian conventional forces from inside Ukraine, but many thousands are still deployed in the vicinity of the border."
Lanzen said that some Russian troops are still inside Ukraine but added that it is "difficult to determine the number."
He said pro-Russian separatists control several border crossings, which allows the routine back-and-forth movement of troops across the border.
Lanzen added that Russian special forces are operating inside Ukraine, "and they are difficult to detect."
Meanwhile, the self-proclaimed Donetsk People's Republic on September 23 claimed that mass graves had been discovered at a warehouse for a coal mine, some 60 kilometers from the city of Donetsk.
Rebels said the bodies of four tortured civilians were found in one of the graves.
Rebels claimed the site had served as a Ukrainian military base.
However, both the National Security and Defense Council spokesman Andriy Lysenko and the National Guard denied ever having control of the mine.
Lysenko dismissed the claim as a "well-planned provocation."
The United Nations estimates more than 3,500 people had been killed since the conflict in Ukraine began in April.
Much of the region's infrastructure and industry have been destroyed by shelling.
With reporting by AP, dpa, Reuters, and Interfax