Security forces erected heavy concrete blast walls and strung barbed wire across two strategic bridges in the capital of Baghdad Friday as heavily armed troops deployed across the city. The security lockdown was meant to prevent a repeat of the events last Saturday, when thousands of demonstrators stormed the Green Zone, the walled-off seat of the Iraqi government.

On April 30, demonstrators denouncing the Iraqi government’s corruption, failure to provide basic services and inability to prevent terrorist bombings pulled down the massive blast walls surrounding the Green Zone, a high-security enclave created by the US occupation authorities after the 2003 invasion of Iraq. They occupied the parliament, breaking up furniture and sending lawmakers fleeing for their lives.

Friday saw no repeat of those dramatic scenes, in large measure because the populist Shia cleric Moqtada al-Sadr, who called on his supporters to join the siege of the Green Zone last weekend, this time urged them to only protest outside the city’s mosques at the end of Friday afternoon prayers.

Sadr, whose Mahdi Army militia waged an insurgency against US occupation troops a decade ago, was called to Iran after the events of last weekend. He had supported the protest ostensibly to further the bid by the US-backed Iraqi prime minister, Haider al-Abadi, to overhaul the current government with the aim of curbing corruption and introducing more competent governance.

It appeared, however, that Sadr was in less than full control of the protest, which followed a series of largely spontaneous actions demanding that the government provide basic services and denouncing its corruption. Last weekend’s attacks on the parliament and assaults on several legislators expressed the bitter hostility of the masses of Iraq’s impoverished population toward a regime dominated by reactionary exile politicians brought back to the country by the US war of aggression.

The storming of the Green Zone shook the Baghdad regime and has provoked serious consternation in both Washington and Tehran, which are both allied with the Abadi regime in the conflict with the Islamic State of Iraq and Syria (ISIS).

Among the security forces occupying Baghdad’s bridges and major roads on Friday were reportedly three regiments of the elite US-trained counterterrorism police, which had been withdrawn from the battle against ISIS to protect the Iraqi regime from the people of Baghdad. These troops, equipped with armored Humvees armed with machine guns, also took up positions inside the Green Zone itself.

On Thursday night, Prime Minister Abadi delivered a televised speech vowing to prevent any repeat of the storming of the Green Zone. A day earlier, he sacked the officer in charge of security in the fortified enclave, Gen. Karim Abboud al-Tamini, who in an earlier protest had been filmed kissing the hand of Sadr in a sign of loyalty to the Shia cleric.

“We fear that some may take advantage of the peaceful protests to pull the country into chaos, looting and destruction,” Abadi said in his televised remarks. “This is what happened in the attack on the parliament and the MPs.”

At the center of the current crisis is the dispute over the attempt by Abadi to replace incumbent ministers drawn from the various Iraqi political parties with a cabinet of “technocrats.” The proposal is bitterly opposed by the politicians and parties that have benefited from the divide-and-rule system imposed by the US occupation, which accorded political positions and influence based on a religious- and ethnic-based quota system.

Shia, Sunni and Kurdish parties all have used their control of different ministries as a means of looting public funds derived from the country’s oil exports, while infrastructure and basic services continued to deteriorate and masses of people were plunged into deepening poverty.

The parliament has blocked Abadi’s appointments, and there are growing calls for his ouster, including from within his own ruling Dawa Party. In one recent parliamentary session, 100 out of the legislature’s 328 members called for the prime minister to resign.

Meanwhile, the Iraqi government is teetering on the brink of bankruptcy, in large part due to the collapse in oil revenues, which are the source of 95 percent of its budget.

Jan Kubiš, the United Nations Secretary General’s Special Representative to Iraq painted a grim picture of the political situation there in a report Friday to the UN Security Council. He said that the country was engulfed in a “profound political crisis” that will only be worsened by the ongoing escalation of the US-led war against ISIS.

Under conditions in which the government is beset by “paralysis and deadlock,” the envoy said, Iraq’s humanitarian crisis is “one of the world’s worst.”

“Nearly a third of the population—over ten million people—now require some form of humanitarian assistance,” Kubiš said. He warned that the US-led assault now being prepared against the ISIS-held city of Mosul would lead to “mass displacement in the months ahead.”

“In a worst case scenario, more than 2 million more Iraqis may be newly displaced by the end of the year,” the envoy warned.

Adding that “political crisis and chaos” would only strengthen ISIS, the special representative told the Security Council that the “demonstrations are set to continue.”

In apparent anticipation of deepening unrest, the Pentagon rushed an additional 25 US Marines to Baghdad to beef up the security force guarding the US Embassy. Located in the heart of the Green Zone, the heavily fortified embassy is the largest such facility in the world, built at a cost of over $750 million and occupying a space roughly equivalent to that of Vatican City.

The political crisis in Baghdad is unfolding even as the US steadily escalates its military intervention in Iraq. The increasingly direct involvement of US troops in the fighting was underscored by the announcement Tuesday of the death of a Navy SEAL in combat with ISIS fighters in the north of the country. And it was announced Friday that US Apache attack helicopters will be sent into combat imminently.

What the simmering protests make clear is that ISIS is merely one of the symptoms of the catastrophe created by the US war of aggression begun in 2003, which claimed the lives of over a million Iraqis and left an entire society in ruins.