Blast rocks police station in Tunis suburb

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In this photo dated Thursday, July 25, 2013, the body of Tunisian opposition politician Mohammed Brahmi is carried into an ambulance at Mahmoud Materi hospital, north of Tunis, Tunisia. Mohammed Brahmi was shot 14 times in front of his home within sight of his family on Thursday, plunging the country into a political crisis and unleashing demonstrations around the country blaming the government for the assassination. (AP Photo)

TUNIS, Tunisia (AP) — A bomb exploded underneath a car in front of a Tunis port police station causing no injuries but representing a dangerous escalation in the country's political crisis.

The blast, in the Tunis port area of La Goulette, came on the day assassinated leftist politician Mohammed Brahmi was set to be buried.

"As we were leaving the station for a routine patrol, we saw a suspicious package under the car," said police officer Mourad Mliki told The Associated Press. "We went back to the station to tell our superiors and there was a huge explosion — it was set off remotely."

The blast shattered windows in the neighborhood and damaged nearby cars. In the aftermath police flooded the neighborhood, setting up checkpoints.

"The explosion was so strong it was like an earthquake," said Walid Khammar, a fish seller living near the police station whose car was damaged by the blast.

The rare explosion in Tunisia comes the day after the government announced that an al-Qaida linked cell was behind Thursday's assassination.

The Interior Ministry, citing physical evidence and witnesses, said Friday that Brahmi's assassin was Boubakr Hakim, a known militant and weapons smuggler that was part of the same al-Qaida linked cell that murdered opposition politician Chokri Belaid back in February.

Hakim allegedly shot Brahmi 14 times outside his home Thursday in full view of his family with the same 9mm semiautomatic handgun used to kill Belaid, before he sped away on the back of a moped.

The assassination has rocked the country and provoked anti-government demonstrations by protesters holding the moderate Islamists elected in 2011 responsible for the lack of security in the country.

Tunisians overthrew their dictator in January 2011, inspiring the pro-democracy uprisings of the Arab Spring across the region. The long-repressed moderate Islamist Ennahda Party dominated subsequent elections and now rules in coalition with two secular parties.

With two political assassinations in less than six months and a faltering economy, the opposition says the government has lost its legitimacy and is demanding a new national salvation government to run the country.

Some 42 members of opposition parties announced late Friday their withdrawal from the 217-member elected assembly charged with completing the countries new constitution.

The opposition accuses Ennahda of turning a blind eye to the rise of ultraconservative Islamist movements known as Salafis, following the revolution — especially those willing to use violence to push their views.

The government had said it did not want to replicate the repressive anti-Islamist policies of overthrown dictator Zine El Abidine Ben Ali but when thousands of salafis attacked the U.S. embassy in September over an anti-Islamic film produced in the U.S., the government cracked down on the movement.

In April, soldiers searching a mountainous region near the Algerian tripped off a roadside bomb causing severe injuries and sparking a search of the region that revealed the remains of training camps and more hidden explosives.

Sandwiched between Algeria and Libya, both home to armed extremists, Tunisia's transition to democracy has been threatened by armed militants and weapons flowing into the country.