Tunisia's Islamist-dominated constituent assembly compromised Saturday in rejecting Islam as the main source of law as it voted on a new constitution for the country that spawned the Arab Spring.

But while it established Islam as the state religion, it promised freedom of conscience, despite one MP warning that "satanists" and "idolaters" would be practicing in public and criticism by a rights group it was too vague.

Saturday's sitting of the National Constituent Assembly, which has adopted 12 out of 146 articles, came amid concerns a January 14 deadline for the charter's approval could be overshot because of disruptions and the slow pace of deliberations.

It was on January 14, 2011, that ousted dictator Zine El Abidine Ben Ali and his family fled the country for exile in Saudi Arabia.

The first two articles adopted, neither of which may be amended, establish Tunisia as a "civil" republic based on the rule of law and with Islam as its religion.

The assembly rejected two amendments, one proposing Islam and the other proposing the Koran and Sunna -- the sayings, acts and judgments of the Muslim Prophet Mohammed -- as "the principal source of legislation".

In what was a raucous session that had to be suspended at one point, Mohamed Hamdi of the small "Current of Love" party defended Islamic law, saying it would give "spiritual backing to all rights and liberties".

But Mahmoud Baroudi, of the secular Democratic Alliance, said the proposed amendments were "against modernity".

Another key precept adopted, Article 6, makes the state the "guardian of religion," "protector of the sacred" and guarantor of "freedom of conscience".

It would also place mosques and other places of worship out of bounds to political activity.

Azed Badi, of the Wafa party, objected, saying the article would "allow satanists and idolaters to organize public events... to spread their beliefs".

But Ennahda's Sonia Ben Toumia countered by saying "Islam is a religion that guarantees freedom of religious practice to others".

And secularist Iyed Dahmani said "those opposed to freedom of conscience want to take us back to dark periods in history when tribunals examined the beliefs of people".

Freedom of conscience article 'too vague'

Yet the Tunisian League of Human Rights was uncomfortable with Article 6. It argued that defining the state as protector of religion and guarantor of things sacred is vague and open to interpretation, which could threaten freedoms.

Approving the new constitution will be a crucial democratic milestone.

Its adoption would end months of political crisis and further distance Tunisia from the chronic instability plaguing other countries in a region rocked by regime change.

Earlier Saturday, assembly speaker Mustapha Ben Jaafar adjourned deliberations for awhile after a leftist member started shouting, demanding he be allowed to speak.

Rowdy scenes on Friday sparked concern the deadline may not be met.

Leading Francophone daily La Presse cited disputes, interruptions and procedural problems.

"Tunisians who expected to see scenes of solemnity as the constitution was being discussed" were disappointed, it said, by "a wild arena in which every cheap shot is permitted".

Elected in October 2011, the assembly was due to have drafted and adopted the text within one year.

But its work was delayed by deep divisions between Ennahda and the opposition, aggravated by a rise in Islamist attacks and sometimes violent social unrest.

The deadlock became a full-blown crisis when suspected jihadists assassinated an opposition MP in July, paralyzing political life.

Ennahda, which has been sharply criticized for failing to rein in jihadists, agreed in October to step down as part of a roadmap brokered by mediators.

Prime Minister Ali Larayedh has agreed to resign, turning over power to a transitional premier, Mohamed Jomaa, but insists a constitution and electoral law are in place first to pave the way for elections this year.

The powerful UGTT trade union, which has been mediating between the two sides, said that should happen by Thursday at the latest.

The assembly is expected to return to its work on Sunday morning.

To be adopted, the constitution will need approval by two-thirds of the assembly's 217 members. Otherwise, it will have to be put to a referendum.