It is hard to tell when it is not independently confirmed  but "Indiscriminate shelling of cities constitutes a foreseeable and unacceptable targeting of civilians," has been the UN Commissioner position as to when a war crime under the Geneva convention may be under way and again Itar reports 
1) The report said almost all the regions have already made known their readiness to receive the people resettling from the Donetsk and Lugansk regions, which have evidenced the scenes of heavy fighting and attacks by pro-government forces on population centers.
2) Earlier on Tuesday it has been reported that two children died in a new attack of the Ukrainian army on the city of Sloviansk. 

“We have information that two children were killed — a 12-year-old boy and a six-year-old girl,” Ilya Suzdalev, spokesperson for the Donetsk Regional State Administration, specified, adding that they died from fragmentation wounds.

A militia representative told ITAR-TASS that there had been victims in Monday's shelling of the city and four houses had been damaged.

“People are being killed every day. The death toll keeps growing,” Stella Khorosheva, spokesperson for Sloviansk's people's mayor, said.

“Ukrainian law-enforcers resumed shelling of Sloviansk late on Monday,” she said. “Several shells exploded in the city center.”

The number of reports mentioning indiscriminate shelling is growing and is a signal among others such as the rhetoric used that the Gov armed forces may be under the influence of the type of mind set leading to war crimes already seen at the Odessa event.

http://en.itar-tass.com/world/735678
http://en.itar-tass.com/world/735585