There have been riots in the Egyptian city of Mansoura after the bombing of a police station killed 14 people and shook the nation.
Adly Mansour, Egypt's interim president, declared three days of mourning and thousands attended a mass funeral in Mansoura, north of Cairo, on Tuesday.
Mohamed Ibrahim, Egypt's interior minister, visited victims in the hospital where he promised that the January referendum to decide on constitutional amendments would go ahead.
"The attacks are an attempt to create a diversion and to terrorize people because of the referendum," he said. "But I want to reassure people that there is a plan in place, in cooperation with the armed forces to protect all of the election centers at the highest level."
Ibrahim said four people had been arrested after admitting their involvement in the attack.
Sections of the five story-building in the Nile Delta city have collapsed after the blast and police evacuated surrounding buildings.
Police said Tuesday that three bombs had been planted before the explosion at the police station, two of which went off at almost at the same time. The third one, found in a car nearby, was defused.
They warned that the death toll from the bombing, which injured 150, could rise because more people might be trapped in the building.
Al Jazeera's Mohamed Fahmy, reporting from Cairo, said Ansar Beit al-Makdis, an armed group active in the Sinai peninsula, had claimed responsibility for bombing. The group, which is also known as Ansar Jerusalem, posted their statement on the Internet, Fahmy said.
Despite the group's claim, riots have reportedly broken out, targeting the Muslim Brotherhood, the Islamist group behind ousted former President Mohamed Morsi, in Mansoura Tuesday afternoon.
Hundreds of people attacked shops and businesses and set two vans reportedly owned by the Brotherhood on fire, according to Al Jazeera's Mahmoud Sobky, reporting from Mansoura.