A bus driving near an army checkpoint in eastern Ukraine was hit by a rebel shell Tuesday, killing at least 10 civilians and wounding a further 13, local officials said.
The Donetsk regional administration, which answers to the central government in Kiev, said in a statement that the rebels shelled the checkpoint near the town of Volnovakha in the Donetsk region while the passenger bus was passing through it.
The press office for military operations in the east said the rockets appeared to have been fired from a Grad multiple rocket launcher.
The Russian news agency Tass cited leading rebel representative Denis Pushilin as saying the report was a "provocation".
"We were not conducting any military actions in that place. There were no clashes there," Pushilin said.
A reporter with Ukrainian television station Channel 5 who reached the scene of the shelling said a teenage girl was among the dead.
The Ukrainian military said roads in and out of areas under separatist control could be closed as a result of the intensification in shelling. The regional administration said bus routes have been suspended after the incident.
Civilian losses of life have occurred on a regular basis since fighting broke out in spring between government forces and Russian-backed militia in the east. The U.N. estimates more than 4,700 people have died as a result of the conflict.
Hostilities have intensified in recent days, jeopardizing hopes for a peace deal.
Separatists and Ukrainian forces have traded accusations of violating a truce that had been in place since early December.
The foreign ministers of Germany, Russia, Ukraine and France were unable to make enough progress in closed-door meetings in Berlin Monday on the Ukrainian crisis to move ahead with a higher-level summit.
German Foreign Minister Frank-Walter Steinmeier said their four-hour meeting was a "very open exchange" but did not produce the results needed for the countries to go ahead with a meeting of their leaders in Kazakhstan that had been proposed for this week.