"New victims are inevitable, I'm afraid."

DONETSK, Ukraine -- Artillery fire in the rebel stronghold of Donetsk killed at least 12 civilians on Friday afternoon, the city hall in the rebel stronghold said, as fighting intensifies between pro-Russia separatists and government troops.

Five people were killed as they were waiting for humanitarian aid outside a community center and two people were killed in the same neighborhood when a mortar shell landed near a bus stop.

By the time an Associated Press journalist arrived at the community center, the bodies were taken away. Nearby trees were cut down by what could have been a projectile.

Five other people died Friday in sporadic artillery fire in the west of Donetsk.

Full-blown fighting between the rebels and government forces erupted anew earlier this month following a period of relative tranquility. Hostilities now seem to be focused around Debaltseve, a railway hub which could prove a crucial link between the rebels in Donetsk and in Luhansk to northeast to it.

While clashes in east Ukraine rage, hopes are still being invested in reviving a peace process that has been undermined with every new day of fighting.

Two rebel representatives went to Minsk for peace talks on Friday, but went back to eastern Ukraine a few hours later after the Ukrainian representative failed to turn up.

Donetsk rebel representative Denis Pushilin insisted that the rebels' ongoing offence is a way to protect the civilians from Ukrainian artillery fire and said they will go ahead with it unless Kiev stops shelling the rebel-held areas.

"The situation has worsened and it is forcing us to go on offensive," Pushilin told reporters in Minsk. "New victims are inevitable, I'm afraid."

Pushilin said they would be ready to resume the cease-fire that was brokered in September and withdraw heavy weaponry, but as long as the demarcation line takes into account the rebels' recent advance.