Interior Minister Mohamed Ibrahim has accused Palestinian Islamist movement Hamas of providing logistical support to terrorists who killed 16 people and injured more than 130 in Mansoura on 24 December 2013.
Ibrahim, who spoke to reporters at a press conference on Thursday, also claimed a Muslim Brotherhood member had admitted to involvement in various crimes in Mansoura and to having links with Hamas.
The Brotherhood was last week officially designated a terrorist group by the Egyptian authorities.
According to Ibrahim, Amer Mosaad, a 30-year-old commerce faculty graduate who "belongs to the Brotherhood," has admitted entering the Gaza Strip via tunnels with Ahmed El-Sayed and Mohamed Ahmed, who are also Brotherhood members, as well as a Palestinian, Mohamed Mahmoud.
Mosaad has admitted receiving weapons training in Gaza, Ibrahim added. He has also admitted committing violent crimes, including opening fire at citizens during protests and other incidents in Mansoura, killing at least one. Brotherhood members Mohamed Ahmed and Ali El-Derini had similarly used firearms, Mosaad added
Ibrahim said that the Brotherhood had expanded its presence under Morsi and had "communicated with its extremist allies in order to execute its aggressive plans."
Assailants communicated with Gaza-based Hamas, which is an ideological offshoot of the Egyptian Muslim Brotherhood, for help and support ahead of the Mansoura bombing, Ibrahim added.
Almost two weeks ago, a suicide car bomb exploded near the security directorate in the Nile Delta's Mansoura, partially damaging the building, a near-by bank, theatre and the city council building.
Sinai-based militant group Ansar Beit El-Maqdis claimed responsibility for the attack. The group has claimed responsibility for other attacks, including an assassination attempt on the interior minister in September.
Ibrahim said the leader of the group in Egypt was Tawfiq Mohamed Freig, also known as Abou Abdullah.
The group robbed Christian-owned jewelry shops to fund the attack, Ibrahim added.
Hamas has denied any links to attacks in Egypt. The allegations are "false and unfounded," and are meant to "drag our name" into the violence, the group said on Thursday.
"The accusations of invovelment in the Mansoura bombing are an attempt to export the internal Egyptian crisis," Hamas spokesperson Sami Abu-Zuhri said via his Facebook page.
Moreover, Ibrahim said militants had penetrated the security services during Morsi's one-year rule, but denied Daqahliya security directorate leaders were complicit in the attack.
Morsi faced criticism while in office for allegedly giving a free hand to militants in the Sinai Peninsula and allying with them. Among other charges, Morsi is to stand trial for collaborating with Hamas and Hezbollah against Egypt.
"Brotherhood allied with the extremist groups during Morsi's one-year-rule," Ibrahim alleged.
Tension is growing before a constitution referendum considered a key milestone in the roadmap adopted by the interim authorities after Morsi's ouster in July.
Ibrahim warned of tightened security measures during the referendum on 14/15 January to protect polling stations and security buildings from terrorist attacks.
"We are determined to confront the terrorist groups and protect the roadmap adopted by the people," Ibrahim said.
A pattern of bombings and assassination attempts has been growing since Morsi's ouster. Police and military installations in the Sinai Peninsula have been the main targets. There have also been an increasing number of attacks in Cairo and the Nile Delta region. Some attacks took place during Morsi's rule, including the killing of 16 soldiers near the border with Gaza.
"This is all happening to return Morsi [to the presidency]. Ask yourselves why this was not happening during his rule?" Ibrahim said.