Waves of bomb attacks and shootings in north of Baghdad have killed at least 82 people, say security and medical officials.
Many of those killed were security forces – who appear to have been a prime target.
One of the worst-hit places was Taji, a Sunni neighbourhood some 20 km (12 miles) north of Baghdad, where at least 18 people were killed.
At least 112 people were wounded on one of the bloodiest days of the year.
Deadly car bombings hit Baghdad, and a government building in Sadr city was attacked. At least seven car bombs hit the northern oil city of Kirkuk.
Waves of bomb attacks and shootings in north of Baghdad have killed at least 82 people
Dhuluiya, Saadiya, Khan Beni-Saad, Tuz Khurmatu and Dibis were also said to have suffered attacks.
The security forces suffered badly in Monday’s attacks, with at least 15 Iraqi soldiers killed in a single attack on a base in Salaheddin province.
Police checkpoints were hit by car bombs, army bases were struck by mortar fire, and one policeman was even attacked in his home.
Those in Taji died in a string of explosions.
“What is the guilt of these poor people?” asked resident Ali Hussein.
“They are working to earn a living. It is a poor market and people were here to shop in this market when the blast happened. Why did this happen?”
It is the deadliest day in Iraq since 13 June, when another wave of bombings killed 84 people and injured nearly 300.
On Sunday bombings south of the capital killed at least 17.
Violence dipped in Iraq following the insurgency in 2006 and 2007, but sectarian violence has returned across the country in recent months amid worsening political tensions.
At least 237 people were killed during June, making it one of the bloodiest months since US troops withdrew in December.
Deadliest attacks in 2012:
• 3 July: At least 40 killed and many more wounded in series of attacks across Iraq
• 13 June: Wave of bombings kills 84 and injures nearly 300 in deadliest day since US troops withdrew last December
• 4 June: More than 20 people killed in bomb attack in Baghdad
• 20 March: At least 45 people die in series of co-ordinated attacks including car bombs in Kerbala city that kill at least 13
• 23 February: At least 55 people killed and hundreds injured in wave of bombings and shootings across the country
• 27 January: A suicide car bomb kills at least 32 and injures about 60 in predominantly Shia Muslim district of Baghdad
At least 44 people have been killed and more than 150 injured in twin suicide car bombings in Damascus, Syria, officials say.
State television said suspected al-Qaeda militants had targeted two security service bases in the Kafr Sousa area.
But the opposition said the attacks – which came a day after Arab League observers arrived – were staged by the government to justify its crackdown.
The Arab League team are tasked with monitoring whether the government complies with a peace agreement that orders all troops to withdraw from the streets, with the aim of ending the violence.
But human rights and opposition activists said the killings continued on Friday, with security forces shooting dead at least 12 civilians.
More than 5,000 people have been killed and thousands more detained since anti-government protests erupted in March, the UN says.
At least 44 people have been killed and more than 150 injured in twin suicide car bombings in Damascus
The two explosions happened within minutes of each other on Friday morning.
Within minutes, state television said two attacks had been carried out by suicide bombers driving vehicles packed with explosives against the General Security Directorate and another branch of the security services in the up market Kfar Sousa district, south-west of Damascus centre.
“Preliminary investigations showed al-Qaeda was responsible,” it added.
Video footage was broadcast of heavily damaged buildings, with rescue workers combing through burnt buildings and blood-stained debris, and ambulances taking the injured away.
The state-owned news channel, al-Ikhbariya al-Suriya, said the first car bomb exploded outside the offices of an unspecified security agency.
When guards at a nearby compound housing the General Security Directorate went to inspect the aftermath of the first blast, the driver of another vehicle rammed the main gates and detonated the bomb it was carrying, the channel said.
“The explosions shook the house, it was frightful,” Nidal Hamidi, a Syrian journalist who lives in Kfar Sousa, told the Associated Press news agency.
“Gunfire was heard immediately following the explosion and windows up to 200m (670ft) away were shattered,” Nidal Hamidi said.
Deputy Foreign Minister Faisal Mekdad told reporters: “On the first day after the arrival of the Arab observers, this is the gift we get from the terrorists and al-Qaeda.
“But we are going to do all we can to facilitate the Arab League mission.”
Faisal Mekdad was accompanied by the Arab League’s Assistant Secretary General, Samir Seif al-Yazal, who said the nine-strong advance team of monitors would not be deterred.
“We are here to see the facts on the ground,” he added.
“What we are seeing today is regretful; the important thing is for things to calm down.”
The US state department condemned the attacks in Damascus but said they must not deter the Arab League observers from doing their work.