Egyptian activist Alaa Abdel-Fattah has been accused of being involved in an arson attack that damaged presidential candidate Ahmed Shafiq's campaign headquarters and called in for questioning.

The Arabic-language news website of Al-Ahram said the move followed eyewitness claims of Abdel-Fattah among hundreds of protesters who marched on the campaign HQ.

Sources added that Bahaa Bastawisi, one of the suspects who was arrested in connection with the attack, said he asked the activist and blogger whether they should set fire to the politician's headquarters and Abdel-Fattah responded positively.

Police are believed to have arrested eight people in connection with the incident.

The arson attack took place after official results for the first round of the presidential election showed that Shafiq, Hosni Mubarak's last prime minister, and Mohamed Morsi, the Muslim Brotherhood's candidate, will face each other in the elections runoff on 16-17 June.

Abdel-Fattah has yet to receive an official document summoning him for questioning.

News that witnesses and suspects have implicated the activist provoked widespread anger on Twitter.

"@alaa abd el fattah slashed my bicycle's tires" a Tweeter user wrote to mock what are regarded as fabricated claims against the activist.

"@alaa abdel fattah burnt my toast", another claimed.

"We have many other activists other than @alaa. Be creative. He's been summoned by prosecutor, AGAIN, for allegedly burning #Shafik HQ!" a Tweeter user said.

Abdel-Fattah is recognised by many Egyptians for his commitment to human rights and criticism of the establishment.

His international profile grew after he was charged, along with 27 other suspects, over the murder of a soldier, stealing weapons from the armed forces and destroying public and private property during a Coptic demonstration in Cairo in October.

The protests, now known as the 'Maspero massacre', turned violent after clashes between protesters and security forces erupted. Twenty-seven people were killed.

While the army accused Christian protesters and Abdel-Fattah of being responsible for the violence, footage aired on Egyptian TV clearly showed security forces vehicles running over protesters.

Abdel-Fattah vehemently denied the charges, saying he did not take part in the protest.

The United Nations Human Rights Commission and Amnesty International called on his release and he was acquitted in December.