The ruling party men were seen dominating the Chittagong City Corporation (CCC) polling centres while the polling agents of other candidates were not found.
The polling agents of BNP alleged that the ruling party men forced them out of the polling centres.
Speaking to Dhaka Tribune, Shakila Akhter and Sumi Akhter alleged that they went to Bakalia Laboratory School as polling agents of BNP-backed mayoral candidate Dr Shahadat Hossain.
"We were driven out of the polling centre. The ruling party men threatened us with dire consequences if we do not go away," they added.
While speaking to the media at the Teachers' Training College polling centre around 10:30am, BNP mayoral candidate Dr Shahadat Hossain alleged that his polling agents were driven out of the polling centres.
"Our agents were assaulted. The electoral environment has been spoilt completely. A one-party rule has been established," said Dr Shahadat.
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Meanwhile, Awami League-backed mayoral candidate Rezaul Karim Chowdhury said that the voters were exercising their voting rights peacefully and spontaneously.
Rezaul said this while talking to media after casting his vote around 9am at Ekhlasur Rahman Government Primary School.
"I am 100% confident of winning the polls," he added.
Referring to the allegations of the BNP, Rezaul said that it is customary on part of BNP to lodge unfounded complaints, sensing defeat in the polls.
Voting in the sixth CCC elections, which was postponed 10 months ago due to Covid-19 pandemic, began on Wednesday around 8 am and will continue till 4 pm without any break.
Other than the two candidates of Awami League and BNP, five other people are contending for the mayoral post this time.
Also, 237 people are contending for the 39 councillor seats and 14 reserved councillor seats for women.
Chittagong Metropolitan Police has marked 417 elections out of 735 as important.