This was stated by NSDC speaker Andrii Lysenko, Censor.NET reports citing Ukrainian News.
"On the night of July 9, terrorists conducted a mortar attack on a checkpoint near the Uspenske crossing point in the Donetsk region. Around midnight, using night vision equipment, the border guards detected an approach of a large group of militants. The attempt to capture the checkpoint was repelled. As a result of the shelling, three soldiers were killed and 4 injured," he said.
Lysenko also added that among the dead is chief of staff of the 5th Battalion who was shot by a sniper.