(CNN) -- A series of explosions and shootings killed 44 people and injured more than 200 in Baghdad and elsewhere Thursday morning, Iraqi police said.
Police believe the wave of attacks, most of them within a two-hour time frame, were a coordinated effort by militants.
While most of the Baghdad attacks targeted majority Shiite neighborhoods, explosions also took place in the majority Sunni provinces of Salaheddin, Diyala, and Mosul.
No militant group claimed responsibility for the attacks, but authorities believe they may be attempts to unnerve Iraqis and erode their confidence in the ability of Iraq's army and police, a police official said.
The country has seen more coordinated attacks since American troops withdrew from Iraq at the end of 2011, the official said.
An Iraqi government spokesman declined comment on the incidents.
But the U.S. Embassy in Baghdad said it "strongly condemns" what it called terrorist attacks.
"These heinous acts targeted people going to work and shopping, children going to school and security forces working to protect the citizenry," the embassy said, adding the attacks were "targeted at all the people of Iraq in a desperate effort to undermine Iraqi society and its institutions."
The United Nations' Assistance Mission in Iraq also condemned the violence "in the strongest possible terms."
"The continuing violent attacks on Iraqis are totally unacceptable and have to stop," said Martin Kobler, special representative of the U.N. secretary-general, in a statement. The attacks "are meant to hinder the achievement of national unity and stability," he said.
In Baghdad, incidents included gunmen opening fire at a police patrol checkpoint, a car bombing in a busy square and an attack at an outdoor market, according to police officials.
Roadside and car bombings were also reported in towns including Hilla, Baiji, Kirkuk and Dujail, police said.
In the town of Mosul, two suspected suicide attackers were shot dead by Iraqi security forces as they were attempting to carry out an attack, police officials said.
The death toll in Iraq has fluctuated over the past four months as U.S. troops completed their withdrawal. In November 185 Iraqis were killed, the majority of them civilians, according to sources within Iraq's Ministry of Interior. In December, that number dropped to 155.
Iraqi government figures for January showed 151 deaths in violence. However, sources with the Ministry of Interior disputed that, saying 293 people were killed.
And the London-based Iraq Body Count group, which tracks civilian deaths, put January's deaths at more than 400.
"The situation is worsening," said Hamit Dardagan, co-founder and principal analyst of the organization. January's figure "shows a constant level of violence that doesn't seem to let up."
While the 2011 death toll -- more than 4,000, according to Iraq Body Count -- was drastically lower than that recorded at the height of the violence, between 2005 and 2007, the group predicted in a January 2011 report that a low level of conflict in Iraq would continue to claim a number of civilian lives for years to come.
Iraq's Sunni, Shiite and Kurdish leaders have squared off in recent months after an arrest warrant was issued for Tariq al-Hashimi, the country's Sunni vice president.
Al-Hashimi is accused of organizing his security detail into a death squad that targeted government and military officials. The warrant was issued shortly after the vice president's Sunni-backed Iraqiya party said it would boycott Parliament, saying Prime Minister Nuri al-Maliki was cutting it out of the decision-making process.
Al-Hashimi last week denied the charges in a televised speech, saying the Iraqi judicial council is under the control and influence of the central government and that the charges are "politically motivated."
Iraqi officials expressed concern Thursday that the violence could cast a shadow over Iraq's hosting the next Arab summit on March 29. The government said earlier this month that logistical and security arrangements had been agreed upon for the event.
The U.S. Embassy said, "We are confident the Iraqi people will remain firm in their desire to keep sectarian division at bay and not allow the terrorists to win or their corrupt vision to triumph over the democratic will of the people."