Ukraine says seven of its troops have been killed in heavy fighting with pro-Russian separatists in the country's east, as President Petro Poroshenko prepares to unveil his plan to quell the conflict.
Reports said fighting appeared to be centered on Krasny Liman and Yampil in the Donetsk region.
Ukraine says 300 rebels were killed, although that figure cannot be verified.
A top rebel commander, Igor Strelkov, reported "heavy losses" in equipment and arms among the separatists.
Meanwhile, Poroshenko is expected to announce a 14-point peace plan on June 20.
According to an unofficial copy published by the media, the plan calls for the creation of a 10-kilometer buffer zone on the border with Russia.
It is also said to include an offer of a unilateral cease-fire by government forces and an amnesty for separatists -- but only if they lay down their arms.
IN KYIV TODAY: Press briefing by the OSCE Special Monitoring Mission in Ukraine (.@OSCE_SMM) at 14:00 local time http://t.co/EhqBjp1VDz
— OSCE (@OSCE) June 20, 2014
Donetsk separatists' flag is well-known. Luhansk apparently has a contest for state symbols: http://t.co/CMJHTmYGPf pic.twitter.com/R22tr5j1l6
— Nikolaus von Twickel (@niktwick) June 20, 2014
12 Ukrainian paratroopers killed near Krasny Lyman http://t.co/rsSSO3jIRr pic.twitter.com/1V8rTaACtE
— Kyiv Post (@KyivPost) June 20, 2014
Turchynov: Operation to shut down Ukrainian-Russian border over http://t.co/mfmbu72vnl pic.twitter.com/WrLcbg8cLU
— Kyiv Post (@KyivPost) June 20, 2014
As #Turchynov says border is sealed off, two tanks and 5 APCs cross into Lugansk oblast in #Ukraine. Interesting interpretation of "sealed"
— Katya Gorchinskaya (@kgorchinskaya) June 20, 2014
More videos app. showing 3 tanks, APCs, white cars entering Luhansk fr East. Not confirmed https://t.co/q6ifuyUDIr http://t.co/JhYCSAlwv1
— Simon Kruse (@crusoes) June 20, 2014
Third attempt overnight by armed separatists to break into #Artemivsk tank base. Attack repelled, but one troop wounded, damage inflicted.
— Christopher Miller (@ChristopherJM) June 20, 2014
#Artemovsk friend in SMS during attack last night: "Massive shooting in Art now, Kalashnikovs and smth much heavier." Reports say RPGs fired
— Christopher Miller (@ChristopherJM) June 20, 2014
More RUS manpads for E Ukraine.Fresh pics from Donetsk oblast http://t.co/7APoEa4BoM Heavy casualties on pro-RUS camp pic.twitter.com/VXebWYO45W
— Ryskeldi Satke (@RyskeldiSatke) June 20, 2014
Luhansk airport comes under fire, militants' combat vehicles enter Luhansk http://t.co/jmoarJ1wUL
— Kyiv Post (@KyivPost) June 20, 2014
Seven Ukrainian servicemen killed, 30 injured in Yampil, Zakotne area http://t.co/Mth0Q4iJU3 pic.twitter.com/rpU5oh776Y
— Kyiv Post (@KyivPost) June 20, 2014
Separatists near #Luhansk tell me they don't trust Poroshenko's ceasefire. Video: http://t.co/qIfxK1c5KL #Ukraine
— Paul Brennan (@paulrbrennan) June 20, 2014