Members of the anti-President Morsi 'Rebel' campaign were assaulted in Cairo on Monday afternoon, allegedly by supporters of the Muslim Brotherhood.
'Rebel' is a grassroots movement to register opposition to President Mohamed Morsi and force him to call early presidential elections by collecting 15 million signatures by 30 June.
Members of the group were collecting signatures in the Helwan district of Cairo when Brotherhood supporters threw glass bottles at them, tore up petition papers and threatened people attempting to sign the petition, 'Rebel' member Mohamed Hussein told ONA news agency late on Monday.
Hussein claimed a female volunteer was dragged along the ground by supporters of the Islamist group and that many other people were injured in the clashes.
The 'Rebel' Facebook page has around 100,500 followers, up by over 30,000 since Monday afternoon.
The positive response has led organisers to expand the campaign to include conferences and roundtable discussions across the country, Mahmoud Badr, founder of 'Rebel', told Al-Ahram Arabic news website on Monday
President Morsi's Islamist allies have attacked the campaign, with some labelling it illegal and unconstitutional.
Officially established on 22 April, the signature drive began on 1 May. Organisers say they have collected more than 2 million signatures so far.