New Delhi: Opposition parties on Wednesday wore black attire inside the Parliament complex to observe a "Black Day", escalating their protest against the Centre over the alleged police action against students and opposition MPs during recent demonstrations.

Leaders from several opposition parties arrived dressed in black as a mark of protest, demanding accountability over the alleged use of force against students protesting the NEET-UG controversy and calling for reforms to the country's education system.

Congress MP Syed Naseer Hussain said the opposition had collectively decided to wear black to register its dissent.

"All MPs of the Opposition parties will come dressed in 'black' clothes today and observe a 'Black Day' in protest over the use of police against the students and the MPs. We want the government to have dialogue with the students and do an overhaul of the education system," he told ANI.

Congress MP Pramod Tiwari also criticised the government's handling of the protests.

"There is a limit to shamelessness. A lathi charge happened on 20 July, and yesterday we protested... People without name tags enter and attack, and the LoP or the opposition just remains seated and does not raise our voice?... You are saying that we are misusing the emotions of the students," he said.

The protest follows Tuesday's demonstrations by Congress leaders, who marched from Rajaji Marg towards Lok Kalyan Marg demanding accountability over the alleged NEET-UG examination paper leak, action against those responsible for the police crackdown on student protesters, and the resignation of Union Education Minister Dharmendra Pradhan.

Congress MPs Rahul Gandhi and Priyanka Gandhi Vadra, along with several opposition leaders, were detained by Delhi Police during the protest before being released later in the day.

As police took the protesters into custody, Priyanka Gandhi criticised the government's actions.

"They are cowards. They are scared. We are not scared of them. They are scared of us," she said while being escorted by police.

Police personnel were seen carrying Rahul Gandhi towards a police vehicle as security forces dispersed demonstrators gathered near Lok Kalyan Marg. Several Congress MPs and party workers were also detained.

Congress Parliamentary Party Chairperson Sonia Gandhi later reached Mandir Marg Police Station, where Priyanka Gandhi had been detained.

The protests stem from the police action during the CJP's 'Sansad Chalo' demonstration in central Delhi on Monday, following which opposition parties accused the Centre of suppressing democratic protests and using excessive force against students and political leaders.