Last week, the government officially changed the Iraqi weekend, adding Saturday to the traditional Friday off.
The government said it would extend the six-hour work day to make up for the lost hours. But many Iraqis ignored the government edict and went to work and school on Saturday to protest.
They want the government to make Thursday and Friday the official weekend instead.
At Baghdad's University of al-Mustansiriya, a statement issued by a student union described Saturday as "the Zionist holiday" and said the government order should not be followed.
General strike declared
It was issued, the statement said, by an interim government that had "expired" after the 30 January elections. The interim government remains in office until a new administration is installed. No date has been set.
"We declare a general strike in the University of al-Mustansiriya to reject this decision and any decision aimed at depriving Iraqis of their identity," the statement said.
In predominantly Sunni Muslim Samarra, 95km north of Baghdad, al-Mutawakil high school opened its doors after fighters threatened to kill its teachers if they took the day off.
"The invaders, the occupiers are trying to impose their principles. This decision is dangerous"
There is no clear cut rule for weekends in the Middle East and other Muslim countries in the region.
In Lebanon, the weekend starts at 11.30am on Friday and includes Sunday. In Jordan, it is Friday and Saturday; Bahrain, Saudi Arabia and Kuwait have Thursday and Friday off, while Iran and Egypt only give Friday off.
On Thursday, students chanting "we don't want Saturday, it's a Jewish holiday" marched to the provincial governor's office in Baquba, 60km northeast of Baghdad.
Police fired into the air to disperse the crowd when a high school student pulled out a hand grenade and started waving it around. At least three students were reportedly injured in the ensuing scuffle.
Sadr City residents ignored the
decree and went to work
In many districts of Baghdad, including Shia-dominated Sadr City, students and civil servants ignored the decree and went to school and work.
At Sadr City's al-Fadhila secondary girls school, all 400 girls showed up for class.
"Sadr City is a Shia Islamic city and we reject Saturday being our holiday because it is related to the Jewish weekend," Saffa Dawud Mahmud, 18, the student union leader said.
She said the student body delivered a letter to the school's
administrators demanding that "Thursday and Friday be the official weekend because both days were blessed in Islam and by sharia", or Islamic law.
The influential Sunni Association of Muslim Scholars, said that by making Saturday a weekend "the invaders, the occupiers are trying to impose their principles" on Iraq. "This decision is dangerous," it added.
In Samarra, one teacher speaking on condition of anonymity, said he had received death threats from fighters warning him not to take Saturdays off.