John Bacon

USA TODAY

The Islamic State claimed responsibility for Sunday's fiery assault at a natural gas plant outside Baghdad that left at least 14 dead, the latest in a series of brutal attacks that left more than 100 Iraqis dead in the war-weary nation.

Four other bomb attacks in and around the capital on Sunday, all targeting commercial areas, killed at least 15 more people, the Associated Press reported, citing Iraqi officials.

The assault at the gas plant began when three car bombs exploded outside the gate in Taji, less than 15 miles north of Baghdad, the BBC said. Suicide bombers and other militants then rushed the plant, clashing with security forces and blowing up gas tanks.

Security forces backed by two military helicopters were able to repel the attack, the government said. Three gas storage tanks were set ablaze at the plant, which produces gas canisters for cooking. In addition to those killed, at least 20 other people were wounded, according to the AP and BBC. Other news outlets reported different numbers of victims, including workers and security forces.

Deputy Oil Minister Hamid Younis said firefighters extinguished the fires caused by the explosions, and the extent of the damage to the plant was being assessed, the AP reported.

ISIL claims responsibility for 3 horrific bombings in Iraq

The other attacks Sunday included a car bomb blast near Latifiyah, 20 miles south of Baghdad, that killed seven people, the AP reported.

The Islamic State, also known as ISIL or ISIS, has stepped up attacks in the nation in recent days. On Wednesday, three separate car bombings in Baghdad killed at least 93 people and wounded more than 150 in one of the deadliest days in Iraq this year.

On Monday, 13 people died when an attacker blew up a minibus in the city of Baqouba, 30 miles northeast of Baghdad.

Iraqi government leaders maintain the attacks are a desperate response to the Islamic State's recent military setbacks in Iraq and Syria, where the militant effort to carve out an extremist Islamic caliphate has stalled.

James Piazza, a political science professor at Penn State who specializes in Middle East affairs, said a political deadlock that has paralyzed the Iraqi government has made Iraq ripe for terror attacks and made "effective and coherent security policy impossible."

Still, Piazza says that that "substantial battlefield reversals" has put a strain on the Islamic State financially and psychologically.

"The loss of territory has deprived them (Islamic State militants) of access to oil resources and other means of financing their organization," Piazza told USA TODAY. He said the military setbacks represented a "demoralizing, symbolic loss" that also threaten the group's international image.

"ISIL is using these high-profile terrorist attacks against symbolically important targets in Iraq, such as Shiite neighborhoods and religious sites, and strategic targets like oil and gas plants, to try to demonstrate that it is potent and attractive to new recruits," he said.

In Syria, the Islamic State is repositioning its forces in the group's de facto capital of Raqqa in response to increasing military pressure from coalition airstrikes and ground forces growing in effectiveness there, U.S. officials say.

"We know this enemy feels threatened, as they should," said Col. Steve Warren, a coalition military spokesman in Baghdad.