BAGHDAD -- Iraq's Prime Minister Nouri al-Maliki said Wednesday he will not relinquish power until a federal court rules on what he claims is a "constitutional violation" by the president to replace him with a member of his own party.

The embattled premier has grown increasingly isolated, with Iraqi politicians and much of the international community lining up behind prime minister-designate, Haider al-Abadi, a fellow member of al-Maliki's Shiite Dawa party. Al-Abadi was picked by President Fouad Massoum to form a new government that can unite the country in the face of an onslaught by Sunni militants.

"Holding on (to the premiership) is an ethical and patriotic duty to defend the rights of voters," al-Maliki said Wednesday in his weekly address to the nation, insisting his actions were meant to "protect the state."

Al-Maliki on Monday vowed legal action, saying he would go to the courts to prove the president's choice of al-Abadi was "a coup" against the constitution.

As international supports mounts for al-Abadi, Iraqi troops imposed heightened security in Baghdad on Wednesday. Tanks and Humvees were positioned on Baghdad bridges and at major intersections, with security personnel more visible than usual as about 100 al-Maliki supporters rallied at Firdous Square.

Widespread discontent with al-Maliki's divisive rule has reached the point where both Saudi Arabia and Iran -- regional rivals often bitterly divided over Iraq -- have expressed support for al-Abadi. The United States, the European Union and the United Nations have also expressed support for new leadership.

In Iran, Supreme Leader Ayatollah Ali Khamenei expressed hope Wednesday that "a government will be formed so that they (Iraqis) can give the necessary and appropriate response to the sedition-makers." Qatar's Ministry of Foreign Affairs expressed hope al-Abadi will establish "a comprehensive national government that includes all components of the Iraqi people."

But al-Maliki, whose bloc won the most votes in April elections, has refused to step down and seeks a third term in office. Al-Abadi was selected by the main Shiite alliance which includes al-Maliki's bloc, the Islamic Dawa party, which says al-Abadi "only represents himself."

At a meeting between al-Maliki and senior military commanders broadcast on state television Tuesday, the incumbent premier warned that security forces should not get involved in politics. He also raised the spectre of further unrest by saying Sunni militants or Shiite militiamen might don military uniforms and try to take control of the streets and "make things worse."

Since June, Iraq has been facing an onslaught by the Islamic State group and allied Sunni militants across much of the country's north and west. Fueled by widespread Sunni discontent with al-Maliki's rule, the insurgency seized Iraq's second largest city, Mosul, and routed beleaguered armed forces. Thousands of people have been killed and more than 1.5 million displaced by the violence.

The militant advance slowed as they approached Baghdad and other majority Shiite areas, but the capital still sees near daily attacks.

On Wednesday, attacks in and near Baghdad killed at least 29 people and wounded scores more, according to police.

A car bomb in eastern New Baghdad killed eight while six people, including four policemen, died when a car bomb struck a checkpoint in western Baghdad. A bomb at a central market killed five people while two died in a bombing in the commercial Karrada district. A car bomb in the Baiyaa neighbourhood killed four and four more died in a mortar attack north of the capital.

The Islamic State's onslaught has uprooted thousands of members of Iraq's Yazidi religious minority after the militants overran their town of Sinjar earlier this month. The Islamic extremists view the Yazidis as apostates and have vowed to kill all those who do not convert.

The Yazidis' plight has prompted a multinational relief effort, with Iraqi and U.S. planes dropping dozens of crates of food and water.

The U.S. has also targeted the Islamic State group with airstrikes aimed at protecting the Yazidis, Christians and other minorities expelled by the Islamic State and to slow the group's advance toward Irbil, the capital of the largely autonomous Iraqi Kurdish region. Another 130 U.S. troops arrived in Irbil on Tuesday on what the Pentagon described as a temporary mission to assess the scope of the humanitarian crisis on Sinjar Mountain.

Australia's Prime Minister Tony Abbott held open the possibility of sending a combat force to Iraq but Defence Minister David Johnston downplayed the prospect of that, saying the military had only committed to sending two C-130 Hercules transport planes for humanitarian aid drops to begin within two or three days.

France said Wednesday it would send arms to Iraqi Kurdish forces and earlier this week, it urged other European states to contribute to the effort.

Associated Press writers Sinan Salaheddin in Baghdad and Adam Schreck in Dubai contributed to this report.