As PPP Chairperson Bilawal Bhutto-Zardari and Co-Chairperson Asif Zardari were grilled by the National Accountability Bureau (NAB) in three corruption cases on Wednesday, scores of charged supporters gathered outside the Rawalpindi office scuffled with security personnel.

Security was tight in Islamabad prior to Bilawal and Zardari's appearance before NAB, with roads leading to the Rawalpindi office sealed off.

PPP workers ─ who had been instructed by party leadership to reach the capital in order to "express solidarity" with their leaders ─ were found awaiting their leaders outside the office in the morning. However, PPP's Nayyar Bukhari alleged that some "peaceful" workers had been stopped at Nadra Chowk, and warned that the administration would be responsible for any "incident".

The father-son duo both consulted their legal team prior to their appearance before NAB. Their entry to the premises was delayed, however, as the workers gathered surrounded their vehicles, making it difficult for them to proceed further.

As they pulled up to the NAB Rawalpindi office, additional security had to be summoned to disperse PPP supporters, who clashed with security personnel as they attempted to force their way into the premises.

The PPP leaders were questioned for two hours in three cases by a combined investigation team (CIT), according to a NAB press release. The CIT also handed them a questionnaire pertaining to the cases, which they must respond to within 10 days.

The duo's responses to the CIT's questioning today, as well as the NAB questionnaire, will be reviewed in accordance with the law, the press release stated, adding that whether or not they will be summoned to Rawalpindi again will be decided in light of their responses.

As Zardari and Bilawal's visit to NAB concluded, the PPP chairperson got out of his car to address his supporters and the media, lamenting his party's "mistake" of not amending the NAB law when it was in power.

"This was our weakness that we did not change this black law which was introduced by a dictator," he told a chanting group of supporters, adding that the PPP would "wipe the Constitution" of every law made by a dictator.

Information Minister Fawad Chaudhry in a video message issued after the incident said that some 500 PPP workers had gathered outside the NAB Rawalpindi office, of which a few dozen had clashed with police, reportedly causing four policemen and two cameramen to be injured.

The information minister alleged that the PPP wanted to teach a lesson to those who had the gall to summon them for the probe by calling on their supporters to "attack" them.

"This is unfortunate. I am hopeful that the PPP and their leadership will apologise for this approach," he stated. "How is this attitude different form that of those banned outfits against whom the NAP [National Action Plan] is being enforced?"

The information minister stated that the Islamabad police had handled the situation with patience and neutrality but after a "certain limit" was crossed, then "of course the state has certain obligations that it will have to fulfil".

"We want cordiality but this certainly does not mean that the accountability process will be stopped," he asserted.

According to the PPP, some 30 political workers were arrested after the tussle with security personnel. Bilawal, in a press conference in the evening, called for their immediate release or the PPP would "take steps".

Condemning the treatment of party supporters, the PPP chairperson pointed out that the government, which was led by a party that had "held Islamabad hostage for 200 days" was unable to "tolerate [PPP] workers for 30 minutes".

Additional reporting by Inamullah Khattak