A bomb targeted an Egyptian military intelligence building north of Cairo on Sunday, wounding four soldiers, the army said, in the second bomb attack on the security forces in the Nile Delta in less than a week.
The bomb went off near an entrance to the building in the village of Anshas, 100 km (65 miles) north of Cairo in Sharkiya province. It partially destroyed the back wall of the building, the army said, describing it as a terrorist attack.
It follows a suicide bomb attack on Tuesday on a police compound in the Nile Delta city of Mansoura that killed 16 people. The army-backed government has said the violence will not derail a political transition plan whose next step is a mid-January referendum on a new constitution.
Sunday's blast, about 80 km (50 miles) north of the site of Tuesday's bombing pointed to the widening reach of militant attacks that have become commonplace since the army deposed Islamist President Mohamed Morsi in July.
Around 350 police and soldiers have been killed in bombings and shootings since Morsi was deposed, most of them in the Sinai Peninsula, where Islamist radicals expanded into a security vacuum left by the Hosni Mubarak's downfall in 2011.
The security forces killed hundreds of Morsi's supporters in the months after his removal, and have arrested thousands more.
Two security sources described Sunday's bomb as an explosive device, while the state-run Nile News TV station said it was a car bomb. Sources previously said it went off in the town of Belbeis, near Anshas.
Five people were wounded by a bomb that went off near a bus in Cairo on Thursday. That bomb appeared to be the first targeting civilians, though there was no claim of responsibility saying what had been targeted.
The authorities say they have defused several other bombs in recent days. On Sunday, police found and defused a crude homemade bomb inside a bag left outside a university building in the Nile Delta city of Damietta.
More attacks expected
Already high political tensions have escalated further since last week's suicide attack. The state declared the Brotherhood a terrorist organization a day later and has arrested several hundred of its supporters in its widening crackdown on the group.
Some analysts say Egypt faces the risk of a protracted spell of Islamist attacks, as well as civil strife fuelled by friction between supporters and opponents of the Muslim Brotherhood: street clashes have killed seven people in the past three days.
The Brotherhood, which propelled Morsi to victory in last year's presidential election, condemned the suicide attack. A radical Sinai-based group called Ansar Bayt al-Maqdis claimed responsibility for that bombing.
The army-backed government has declared itself in “a war on terror” as it steers Egypt through the new political transition plan expected to yield presidential and parliamentary elections next year.
Army chief Abdel Fattah al-Sisi, who led Morsi's overthrow, is widely seen as the favorite to win that election, though he has yet to declare his candidacy.
Ansar Bayt al-Maqdis has claimed responsibility for other major attacks since Morsi's downfall, including a failed attempt to assassinate the interior minister in September.
The group emerged in North Sinai after Mubarak's downfall, mounting attacks including a string of bombings targeting a pipeline used to export gas to Israel and Jordan.
“There will be more [attacks]. I don't think that any factor has changed that would lessen the attacks at least in the short-term,” said H.A. Hellyer, a Cairo-based fellow with the Royal United Services Institute.
“Those that oppose the army and want to see Morsi's reinstatement go beyond the Muslim Brotherhood - and it is likely some non-Brotherhood Islamists have turned to violence, including, but not exclusively, those within the Ansar Bayt al-Maqdis group,” he said.