Heavy shelling in Ukraine's rebel held east

(Vatican Radio) The heaviest shelling in recent weeks has shaken the main city in Ukraine's rebel-held east.  Sunday's clashes heightening worries about the renewal of a full-scale conflict between government forces and pro-Russian separatists. 

Witnesses said artillery explosions roared throughout the early hours of Sunday in rebel-controlled Donetsk city, quietening only after sunrise. 

Local authorities said four residential buildings were destroyed but it was not immediately clear how many people were killed or injured.

Listen to this report by Stefan Bos

The latest violence came shortly after Ukrainian President Petro Poroshenko called last week's elections in areas held by pro-Russian separatists a "farce". 

He made clear that the presidential and parliamentary poll in the unrecognized Donetsk and Luhansk 'Peoples Republics' threatened the entire peace process. 

"We will continue the intensive reinforcements and widening our defense capabilities in case the situation develops contrary to our wishes," he warned the rebels.  

The clashes underscored international concerns over massive violations of the cease-fire called on September 5. Some of the heaviest fighting focuses on Donetsk's airport.

Residents are in the crossfire. Funerals were held for teenagers Andrey Eliseev and Daniil Kuznetsov, who were killed last week while playing football, recalled their teacher. 

“Ukraine isn’t killing dogs, it’s killing people!", she cried "Why is everybody silent, why does nobody see us? Why do our children have to die? Why are we left to pray?” 

Kiev suggests the artillery shell that killed the boys came from rebel held areas. It also claims Russia supports separatists with tanks and troops. 

Moscow denies those allegations, but reporters witnessed scores of military vehicles moving near Donetsk and farther to the east. Many of the unmarked vehicles were seen towing artillery and some even troops.