Thousands of Muslims turned out to march toward a meeting of Indonesian parliamentarians to demand they incorporate Islamic law into the constitution.

In one of Jakarta's largest demonstrations in months, 4,000-5,000 men and women marched peacefully through the city's banking district on Saturday toward the legislature where the annual session of the People's Consultative Assembly, the country's highest constitutional body, was meeting.

"Save Indonesia with Islamic Law," read their banners. Many were written in Arabic. They shouted "God is great" as they filled two lanes of the road, with men at the front of the protest and women in traditional Muslim headcoverings toward the rear.

The protesters said they were from Hizbut Tahrir Indonesia, or the Liberation Party.

"Islam has an ideology like capitalism and communism, but Islam is better," said one marcher, Hamzah Salahudin, 33. He said they were walking to the assembly building. "We will convey our aspirations and demand Islamic law," he told AFP.

A statement issued by the demonstrators said Indonesia's crisis of poverty and unemployment, its high number of school dropouts, increasing crime and moral decay have resulted from the absence of an Islamic system, as well as from bureaucrats who fail to carry out their duties properly.

At the 10-day assembly session which began Thursday, legislators are discussing proposed constitutional amendments, one of which calls for the implementation of Islamic law, or Sharia.

At its congress last month Indonesia's largest Islamic organization, Nahdlatul Ulama, passed a recommendation opposing efforts to make Islamic law compulsory for Muslims.

The constitution's Chapter 29 says the state guarantees every resident's freedom to adhere to their respective religions and to perform their religious duties.

But the United Development Party, the largest Islamic political party headed by Vice President Hamzah Haz – and several smaller Islamic parties – are pushing for the Sharia amendment.

More than 80 percent of Indonesians are Muslim but other faiths are widely accepted.

Last month hundreds of people from Hizbut Tahrir rallied outside the Philippine embassy in Jakarta to shout their objections to the jailing by a Philippine court of an Indonesian man on explosives charges.