Baghdad (CNN) -- Protesters calling on Iraqi lawmakers to approve the national budget took to the streets of Baghdad on Tuesday, prompting security forces to shut main entrances into the city.
The protests focused on the heavily fortified green zone in central Baghdad. They were spurred and organized by radical Shiite cleric Muqtada al-Sadr.
In response to the demonstrations, security forces blocked all bridges between two main sections of Baghdad, and sealed entrances into the city proper, police officials said.
Authorities were concerned the number of protesters could grow.
Demonstrators are demanding movement on the $115 billion budget that was approved by Iraq's Cabinet in October. Parliament still needs to pass the draft legislation, and leaders of key political parties are struggling to reach an agreement.
Kurdish Lawmaker Mahmoud Othman told CNN the main sticking point in negotiations is the amount allocated to oil service companies working in Iraq's semiautonomous Kurdistan region.
Despite vast reserves and reliance on oil for government income, exploration in Iraq has been hindered by decades of conflict.
With the world's fourth-largest oil reserves, Iraq's government depends on oil revenues to fund more than 90% of its budget.