At least 11 people were killed and more than 100 others were wounded in a massive explosion at a security compound in Egypt's Nile Delta town of Dakahlyia on Tuesday, a month before a vote on a new constitution key to the transition from military-backed rule.
Cabinet spokesman Sherief Shawki blamed the blast on the Muslim Brotherhood group of former Islamist President Mohamed Morsi and said Prime Minister Hazem el-Beblawi had officially declared the group a terrorist organization.
A security source said the blast may have been caused by a car bomb, but it wasn't clear whether it was suicide attack or not.
State TV said that at least 11 people were killed and that more than 100 others were hurt. It said that the attack was the worst in the city's history and that two senior security officials were among the wounded.
Another security source it was still unclear what caused the explosion, "but it seems to be a big one that led to the collapse of parts of the security building."
Suicide attacks on soldiers and police have sharply risen in Egypt since the army ousted Morsi in July amid mass unrest against his rule.
In overthrowing Morsi, the army set out a political road map that is supposed to start with a mid-January vote on a new constitution and to be followed by presidential and parliamentary votes.
The state-run Middle East News Agency quoted el-Beblawi as saying those responsible for blast "will not escape punishment."
Brotherhood officials, most of whom are on the run or out of the country, couldn't be immediately reached for comment on the government charges.
Witnesses in Dakahlyia said many cars inside and outside the security compound were burned out and the entire city was in chaos as people were hurrying to hospitals to check on victims.
Egypt's Nile News TV cut into its late-night programming to urge people to go to hospitals to donate blood to the victims.
Most bomb attacks since Morsi's overthrow have occurred in the Sinai region, which borders Israel and the Palestinian Gaza Strip. Around 200 soldiers have died in Sinai since July.
Interior Minister Mohamed Ibrahim survived a suicide car bomb attack targeting his convoy near his home in Cairo last September.
Egyptian media and many army and state officials have blamed all the violence on Morsi's Brotherhood, the state's oldest and most organized Islamist group, which has won all five elections since a 2011 uprising that ousted longtime President Hosni Mubarak.
Morsi's dramatic exit triggered a wave of violence that started with police attacks on his supporters' two main camps in Cairo on August 14 in which hundreds were killed.
That violence prompted a wave of attacks on churches and police stations. Thousands of Islamist activists have been arrested in the unrest and around 100 policemen killed.
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