Four Ukrainian soldiers died overnight Sunday and Monday morning during intense clashes with Russian-backed rebels in the contested region of Donbas, according to a report by the pro-Ukrainian news web site Unian. The deaths came after February’s Minsk II ceasefire agreement was breached around 140 times within 24 hours.

"In the last day, there has been a certain intensification of the enemy attacks in the direction of Mariupol, where a lull had been observed over the last few days," said a statement from Ukraine's Anti-Terrorist Operations.

Kiev’s government, which has branded pro-Russian rebels in the Donetsk and Luhansk regions of eastern Ukraine as terror groups, said the attacks took place between 6 p.m. Sunday and the early hours of Monday morning. Most deaths came as a result of troops being bombarded by shells from banned heavy weapons such as 120 mm mortars and tank fire.

Ukrainian government troops, along with volunteer battalions, said they were attacked as many as 99 times on Sunday and Monday near the villages of Pisky and Optyne, and the town of Avdiyivka. Pro-Russian rebel authorities said they were attacked 41 times over the same period, but experienced no deaths or injuries.

The Ukrainian military last month violated the ceasefire in 1,300 cases, Eduard Basurin, spokesman for the rebel Donetsk republic’s defense ministry, said Monday. "July’s bombardments left 22 people killed and another 29 injured," the Donetsk News Agency quotes Basurin as saying. He added that the Donetsk republic’s army lost five men and had 10 wounded, while 17 civilians died and 19 were injured.

Since the war in eastern Ukraine began in April 2014, more than 7,000 people, military and civilian, have been killed.