Supporters of former disqualified presidential candidate Sheikh Hazem Salah Abu Ismail reportedly surrounded the Cairo headquarters of the al-Wafd Party before setting the building on fire.
Eyewitnesses told Arabstoday that the premises, where the daily al-Wafd newspaper is also published, were cordoned off and security forces used teargas to disperse the protesters.
Al-Wafd editor-in-chief Sayed al-Nasser told Arabstoday, that supporters of the Islamist figure had broken into the al-Wafd head office before security forces arrived. He added that many of the staff members suffered breathing problems due to the teargas.
The editor also criticised security forces for failing to protect the premises and allowing the mob to break down the metal gates and enter the newspaper office. "Where are the security authorities that should be guarding the newspaper premises?" he asked.
Al-Nasser claimed that pro-Abu Ismail protesters directed "vile abuse" at the newspaper staff.
Meanwhile, the Supreme Press Council has condemned the attack on the headquarters of the newspaper.
In a press statement, the Council demanded that authorities provide the necessary protection for all partisan, private and national newspapers which received threats, stressing its full solidarity with all journalists in the face of any threats and calling for the quick arrest and trial of the assailants in these attacks.
Followers of Abu Ismail have denied any connection with the attack.