Sunni jihadists captured two strategically located towns in Iraq's western Anbar province Saturday as government forces and armed Shiite militiamen failed to stave off the militants. 

The Islamist militants of the al-Qaida-affiliated group Islamic State in Iraq and Syria (ISIS) captured the border town of Qaim, which is near Syria, and Rawah, which is on the Euphrates River. Their captures reveal the waning power of Prime Minister Nouri al-Maliki's government, which has failed to fend off the extremists and allied militants, The Associated Press reported. The militants began their offensive when they successfully captured the city of Mosul last week. 

Sunni militants and other insurgents have been pushing back against al-Maliki's majority Shiite government, which has been accused of excluding Sunnis and Kurds. Now, Shiite fighters are pushing back against the Sunnis, indicating that the country could be heading toward a sectarian civil war. 

Sunni militants have controlled the city of Fallujah, in Anbar, since January. The fighting in Anbar province has disrupted the use of a major highway that links Baghdad, Iraq's capital, to Jordan's border. 

Around 20,000 Shiite militants armed with combat gear, assault rifles, machine guns and rocket launchers took to the streets of Baghdad on Saturday following Shiite cleric Muqtada al-Sadr's call to arms. The cleric once led a militia against U.S. troops and is blamed for a mass killing of Sunni citizens during a sectarian war in 2006. 

Police and army officials in Iraq said 30 Iraqi troops were killed during clashes Friday. 

Lt. Gen. Qassim al-Moussawi, the chief military spokesman, confirmed to the AP that Qaim had fallen, but said tribesmen are trying to clear the city of the "terrorists."

Rawah Mayor Hussein AIi al-Aujail said Sunni militants seized and raided government offices in the town, which is 175 miles northwest of Baghdad. 

The militants' capture of the border crossing in Qaim enables them to move weapons and equipment to different areas. 

The White House has criticized the besieged al-Maliki government, with Obama saying Friday that the prime minister needs to form a more inclusive government. However, Obama did not say al-Maliki should step down. 

"Only leaders that can govern with an inclusive agenda are going to be able to truly bring the Iraqi people together and help them through this crisis," Obama said, according to the AP. 

Obama also announced Thursday that he is deploying up to 300 military advisers to help stop the violence in the country. The advisers will join 275 troops in Iraq to provide security for the U.S. Embassy. Obama was clear, however, that U.S. troops will not return to combat, though he did not rule out the possibility of airstrikes. 

U.S. officials say manned and unmanned American drones are flying over Iraq on intelligence missions. 

Grand Ayatollah Ali al-Sistani, the voice of the country's Shiite minority population, joined in calls for al-Maliki's ouster. 

Al-Sistani's comments, delivered through an aide, could signal the beginning of the end of al-Maliki's power. Al-Sistani called for a new parliament to be set up among the political coalitions that won seats in the April 30 election. He said it was important that the coalitions form "an effective government that enjoys broad national support" and "avoids past mistakes."

Al-Sistani's calls to defend the country, and particularly Shiite shrines, has made it appear like the sectarian clashes is a religious war, but al-Sistani's aides said the cleric is addressing all Iraqi citizens, not just Shiites. 

Al-Maliki's State of Law party won the most seats in the April parliamentary elections, but his supporters must form a majority coalition in the new 328-legislature, which could lessen his hold over the government. 

If al-Maliki steps down now, President Jalal Talabani, a Kurd, will take al-Maliki's position until a new prime minister is elected. However, Talabani is in Germany, suffering from ill health, so his deputy, a Shiite named Khudeir al-Khuzaie, would likely take his place. 

Names being floated by Shiite politicians as potential replacements for al-Maliki include former Vice President Adel Abdul-Mahdi, a French-educated economist and Shiite; Ayad Allawi, a secular Shiite who was Iraq's first prime minister after Saddam Hussein hell; and Ahmed Chalabi, a one-time favorite in Washington to lead Iraq.