At least one person was killed and three others were wounded after the Ukrainian forces shelled the city center of Donetsk, the head of the Donetsk People's Republic (DPR) Denis Pushilin said Saturday.

"There are three injured and one dead," Pushilin told Russian broadcaster Rossiya 24, revealing that the Ukrainian forces have initiated two waves of attacks on the DPR city so far.

The shelling of Donetsk is an attempt to disrupt the referendum on joining Russia in the region, Pushilin highlighted. 

The voting in the referenda on Russian accession of the Donetsk and Lugansk People's Republics, as well as the Zaporozhye region, began early Friday.

The subject of having the referenda promptly was addressed earlier this week by the DPR and LPR public chambers, making official appeals to the rulers of their respective republics on Monday. A day later, the referendum dates were determined, and local legislatures overwhelmingly enacted referendum laws, while elections officials authorized the procedure.

Russian President Vladimir Putin announced Russia's formal recognition of the independence of the DPR and LPR in late February. This led to Ukraine escalating against the republics and using various tactics to try and undermine their leadership and hurt their civilians. That same month, Ukraine shelled a hospital in Donetsk and caused the death of eight civilians in another strike on the region.

In early August, Central Donetsk has been undergoing some mine clearance works that have been threatening civilians, and since Ukraine has been equipped with NATO;s Tochka-U tactical missile systems and long-range rocket systems, the number of civilian casualties in the DPR more than doubled.

On the eve of the vote, the format of the plebiscite was the source of much debate according to TASS. Due to time constraints and technological concerns, it was decided to use traditional paper ballots rather than digital voting. For security considerations, in-person voting will be limited to September 27, with voting arranged in communities and door-to-door on the remaining days.

DPR and LPR residents will be asked if they "support their republic's accession to Russia as a federal subject."

Residents of Zaporozhye and Kherson will be polled to see if they "favor the region's secession from Ukraine, the creation of an independent country, and subsequent accession to Russia as a federal subject."

Ballots will be printed in Russian in the DPR and LPR, where Russian is the only recognized state language. The question will be presented in both Ukrainian and Russian in the Zaporozhye and Kherson areas.