Pakistan Peoples Party Chairperson Bilawal Bhutto-Zardari on Friday vowed to challenge what he believes was 'rigging' in the by-election for Sindh Assembly constituency PS-11 (Larkana-II).

Voters had headed to the polls on Thursday, with Grand Democratic Alliance (GDA) candidate Moazzam Ali Abbasi emerging as the winner according to unofficial results.

By-elections in PS-11 had been announced by the Election Commission of Pakistan (ECP) after the Supreme Court had de-seated Abbasi in August.

Polling was held in a peaceful environment and no untoward incident was reported anywhere in the constituency. Special security measures were put in place, including deployment of Rangers and the army in the constituency, in addition to the police. Polling had begun at 8am and continued till 5pm without break.

As per preliminary results from 138 polling stations that were set up for the by-election, Abbasi bagged 31,557 votes, while his rival Jamil Soomro of the PPP obtained 26,021 votes.

Following the voting process yesterday, Bilawal had said in a post shared on Twitter that: "We will challenge this rigging at every forum. The truth can’t be hidden. We will expose this selection. We will have a re-election and take back this seat."

In a series of posts shared on Twitter, the PPP leader said he was proud of PPP workers for "fighting an honorable election," which he claimed they did "despite immense pressure from the establishment. From pre-poll with NAB arresting & sending notices to PPP workers & their families".

"On polling day, Rangers took over the inside of polling stations. harassed our women voters, threw out our polling agents, and deliberately slowed polling. Women polling stations where PPP performs well were purposely started hours late," he alleged.

The PPP chairperson added that media had been reporting that women voters were threatened to vote for GDA.

"Despite our pleas, ECP did not take notice."

Further, Bilawal said that the PPP candidate wasn't allowed inside polling stations.

"We kept asking ECP to intervene but its malafide intent was apparent in its silence."

He also said that, "despite the political engineering", PPP had reduced the lead of other parties by 5,000 votes in less than a year and vowed to challenge the 'rigging' at every forum.

Separately, GDA supporters had raised objections over the visits of elected representatives of the PPP, including Bilawal, Khursheed Ahmed Junejo and Nadir Magsi, to various polling stations, pointing to election commission rules that place curbs on political activity near polling stations.