Donetsk (Ukraine) (AFP) - Ukrainian troops and pro-Russian rebels clashed Friday around the flashpoint city of Donetsk, while trading blame over the death of a Swiss aid worker, four weeks into their shaky truce.
Parliament speaker Oleksandr Turchynov accused insurgents of breaking the ceasefire "over a thousand times", while the military claimed that Russian military specialists were reinforcing rebel positions.
The deadly shelling of the International Committee of the Red Cross (ICRC) office in Donetsk, which prompted a firm rebuke from UN Secretary General Ban Ki-moon, was an "act of terror", Kiev said, blaming rebels who control the city.
"This terrorist act cannot be justified," Ukraine's foreign ministry said in a statement on the death of the 38-year-old Geneva-based ICRC employee. Kiev's military said the rebels had repeatedly fired on central Donetsk "to discredit the anti-terrorist operation."
Kiev also accused the insurgents of firing shells that hit a school bus and nearby bus station on the first day of classes in Donetsk on Wednesday, killing 10 civilians.
However, Russia and the rebels both accused Ukrainian forces for the Red Cross worker's death.
"The Ukrainian army is firing at Donetsk for the second day in a row from Uragan (Hurricane multiple rocket launcher) systems," Andrei Purgin, deputy prime minister of the self-proclaimed Donetsk People's Republic, told AFP.
"Firing from such systems is not targeted. They simply hit a general area, along with everyone in it," he said, adding that the strike most likely originated from Krasnogorovka, a town 20 kilometres west of Donetsk.
Russian foreign ministry spokesman Alexander Lukashevich echoed Purgin, saying the fire came from positions controlled by Ukrainian soldiers and calling for a full investigation.
"In Kiev they didn't want to admit the obvious: the area of Donetsk that came under fire is under control of rebels and the shelling came from positions occupied by Ukrainian forces," the Russian ministry spokesman said.
- Battle for Donetsk airport -
The fighting in Donetsk, a coal mining hub that was once home to nearly a million people, resumed after a relatively quiet night Friday in several neighbourhoods, according to city hall, which said five civilians had been injured over the past 24 hours.
AFP journalists heard two loud explosions in the city centre Friday morning.
Kiev said the rebels were getting considerable reinforcements for their push to capture the Donetsk airport in the north of the city.
"Our reconnaissance observed the arrival of considerable armour, heavy artillery and soldiers into this area," said army spokesman Andriy Lysenko.
"Russian forces have moved a unit of unmanned aerial vehicles to the airport area for reconnaissance, which are operated by Russian specialists," he told journalists.
The international hub was completely rebuilt at a cost of nearly $1 billion for Ukraine's hosting of the 2012 Euro football championships, but has been shut down and heavily damaged since May.
Its long runway could eventually give rebels the ability to land large planes, although Kiev said last month that the damaged facility would be unable to service or fuel aircraft.
Locals said they had observed no change since the truce was signed.
"We've been under fire since May 26," said 78-year-old Raisa Golovichkina. "Both sides are guilty of all that's happened to us."
- Western fears -
With the toll from five months of fighting standing at more than 3,200 people, the UN secretary general said he was "saddened and disturbed" about the aid worker's death.
"The Secretary General is seriously concerned over the dangerous surge of fighting," Ban's spokesman said. "These recent tragic incidents underscore the fragility of the current ceasefire," he added.
"Political and diplomatic efforts must be urgently redoubled toward this end," he said.
The European Union also expressed concern over the state of the ceasefire. Ukrainian authorities say 71 soldiers and civilians have died since an initial peace deal was signed September 5. No figures are available for losses among the insurgents.
Under the terms of a September 19 truce that followed, Kiev and the rebels are meant to withdraw heavy weapons from a 30-kilometre (18.6 miles) buffer zone along the eastern front line.
But Lysenko, the military spokesman in Kiev, said the rebels' failure to halt fire meant that "the Ukrainian side was not withdrawing its weapons and continuing to defend its position."