The Committee of Voters of Ukraine (CVU) says that elections may need to be held again in a number of populated areas. CVU Project Manager Marysia Zakharchenko said this during RFE/RL's Ukrainian Service's election TV-marathon.
According to Zakharchenko, besides Mariupol, where polling stations have not yet opened, there are also problems in Krasnoarmiysk, in Donetsk Oblast.
"In Krasnoarmiysk, we noted that the territorial election committee received ballots, but didn't give them to district election committees, because they questioned these ballots," she said.
"There are problematic districts in Kyiv Oblast as well. Besides this, there is also Dnipropetrovsk -- the CVU recorded violations of the election process there," Zakharchenko added.
Earlier, the CVU also reported that the election process in Svatov, Luhansk Oblast, may be disrupted.
As of 3 p.m. local time, 33 percent of Zaporizhzhya citizens had voted, Hromadske TV reports.
The head of the Luhansk Military and Civil Administration, Heorhiy Tuka, has shared photos of a polling station in Lisichansk, Luhansk Oblast. According to him, the building is in terrible condition and lacks basic utilities, including heating, toilets, and a kitchen.
"The political mood of the city authorities is irrelevant. But the attitude towards people is beastly," he wrote on Facebook:
Election officials at a polling station in Vynohradivskyy District, Zakarpatska Oblast, have done their best to make the place cozy:
Voter turnout across Ukraine as of 4 p.m. local time was 36.2 percent, according to the Opora civic network.
The highest turnout is in Ukraine's west (38.1 percent), while the lowest is in the south (32.6 percent).
Polling stations are to close at 8 p.m. local time, which is in about two hours.
Odesa law-enforcement officers have detained a bus with 34 men and their coordinator for bribing voters, according to the official Twitter account of the Ukrainian police.
The most common violation of the voting process in Odesa is disregarding the secrecy of the ballot. Such violations have been recorded at almost 9 percent of polling stations, Ukraine's Committee of Voters reports.
This video posted on YouTube shows some Odesa locals seemingly filling in their ballot forms on a window sill, even though the law states that voting may only take place in a voting booth.
Election observers have a special designated area at a polling station in the western city of Rivne.