Sunni leaders in western Iraq have called for Maliki, a Shiite, to be removed from power. Elections in the country are set for April in a fracturing internal political climate.
The Iraqi Ministry of Defense said Wednesday it closed a border crossing to Jordan without providing an official explanation.
Hikmat Suleiman, a Sunni council leader in Anbar province, said the border closure was to put pressure on protesters. Local leaders expressed similar sentiments, saying the central government was waging an economic war on the anti-Maliki movement, reports al-Arabiya.
Martin Kobler, U.N. special envoy for Iraq and head of the assistance mission there, called on opposition movements across the country to ensure their demonstrations are carried out peacefully.
"We call on the protesters to refrain from violence and to maintain the peaceful character of their demonstrations and on the security forces to show the utmost restraint in maintaining law and order," he said in a statement.
The BBC reported last week that influential Shiite cleric Moqtada Sadr has thrown his support behind the Anbar protest movement.
Political tensions have simmered in Iraq at least since U.S. forces left the country in December 2011.