At least 14 people were killed and 250 others wounded Tuesday in a car-bomb attack on security headquarters in the Nile Delta city of Mansoura, Egyptian officials told Efe.

At just 20 days from the referendum on a new constitution, the military-led provisional government said that this attack will not alter the road map to transition.

More than a score of ambulances rushed to the scene of the bombing, while the governor of the surrounding Dakahliya province, Omar Shawadfi, made a call for blood donations to help the wounded.

The powerful explosion at around 1:00 a.m. destroyed much of the front of the police station and of adjacent buildings, including Mansoura city hall, a theater and a bank branch.

Amid the tense atmosphere, police blocked an attempted jailbreak at a nearby prison, while many people gathered to provide support for the security forces and attacked properties believed to belong to Islamists in revenge for the bombing.

From Mansoura, Interior Minister Mohamed Ibrahim said that "the perpetrators of this attack, whether the Muslim Brothers or any other extremist group," will be pursued.

The violence was unleashed as Egypt prepares for a referendum on the new constitution on Jan. 14-15, as part of the plan created by the military after they ousted President Mohammed Morsi, leader of the Muslim Brotherhood's political wing, on July 3.

Assuming the new charter is approved, the military regime plans fresh presidential and legislative elections.

The Muslim Brotherhood slammed Tuesday's attack "against the unity of the Egyptian people," and said the government is trying to make use of the incident to spread instability.

Since the coup d'etat against Morsi, Egypt's first democratically elected head of state, the number of attacks have increased against security forces, who in turn have killed hundreds of Muslim Brotherhood supporters protesting against the putsch. EFE