Deputy Interior Minister Serhiy Sarovy said on June 6 that separatists who had taken up a position in a church near Slovyansk launched a mortar attack on a security checkpoint.
One police officer was killed and two injured in that attack.
The separatists also claim they shot down a Ukrainian surveillance aircraft near Slovyansk.
Purported amateur video footage posted on the Internet appeared to show an aircraft falling down, one of its engines on fire.
The reports claimed that the An-30 surveillance plane came down a few kilometers east of the city.
The claims could not be immediately confirmed.
WATCH: A video purportedly showing the downing of a Ukrainian surveillance plane
White House official says Obama told Putin that if #Russia works with new Ukrainian Government there could be openings to reduce tensions
— Sky News Newsdesk (@SkyNewsBreak) June 6, 2014
French President Francois Hollande tells D-Day veteran "we made Ukraine and Russia talk" and says he wants ceremony "to be useful"
— Sky News Newsdesk (@SkyNewsBreak) June 6, 2014
Look at Johnny-no-mates on the right and the attention the nice old lady on the left is getting HT @BDStanley pic.twitter.com/rStTl42cD6
— john sweeney (@johnsweeneyroar) June 6, 2014
The unidentified official said today that the negotiations are to take place from June 7 to June 9.
The official also said Kyiv is considering paying off debts for last year's Russian supplies.
A spokeswoman for the EU’s energy commissioner told the ITAR-TASS news agency that the dates for the talks have not been confirmed yet.
The two sides differ on how much is owed by Ukrainian state energy company Naftohaz and the pricing for Russian gas.
Russia more than doubled the price Ukraine has to pay for gas -- to nearly $500 per 1,000 cubic meters -- after pro-Russian President Viktor Yanukovych was ousted in February.
Gravity of the moment there, Putin aside from others, Poroshenko on the other end pic.twitter.com/fBYJJJx1kP via @pavelsheremet
— Ryskeldi Satke (@RyskeldiSatke) June 6, 2014
Happy together. Merkel & Putin today for #DDay70 ceremony. http://t.co/N88htmy46T pic.twitter.com/7Mgs6ElSqe
— Jim Roberts (@nycjim) June 6, 2014
MT @ADeshchytsia. On 70th anniversary of #DDay70, let's not forget that 1/4 of all Ukrainians died in WW2. Highest ratio of any nation?
— Gulliver Cragg (@gullivercragg) June 6, 2014
Putin and Poroshenko met briefly on the sidelines of D-Day anniversary events in France today.
It was Putin's first meeting with Poroshenko since he was elected president of Ukraine on May 25.
Putin also held informal talks with U.S. President Barack Obama on the sidelines of the ceremonies.
The events to mark the 70th anniversary of the D-Day landings of Allied troops in Normandy came amid a deep rift between Russia and Western nations over Moscow's actions in Ukraine.
The events were preceded by intense diplomacy in the hope that the gathering of world leaders would lead to a thaw in tensions.
Voice of America: Putin, meets Obama, Poroshenko on D-Day event sidelines http://t.co/Fcd2mVoEWg
— Kyiv Post (@KyivPost) June 6, 2014