Baghdad - Six explosions battered Shi'ite and Sunni Muslim neighbourhoods across Baghdad on Thursday, killing at least 14 people and extending a descent into the worst sectarian violence since the civil war five years ago.
The bloodletting reflects increasing tensions between Iraq's majority Shi'ite political leaders and the Sunni minority, many of whom believe they have been unfairly treated since the 2003 fall of Saddam Hussein, a Sunni.
But the civil war in Syria between Sunni rebels and President Bashar Assad, whose Alawite sect derives from Shi'ite Islam, has aggravated the strife in Iraq. Sunni and Shi'ite Iraqi fighters alike have been crossing the border to fight on opposing sides in Syria.
No group claimed responsibility for Thursday's attacks, but Sunni Islamist insurgents and al-Qaeda's Iraqi wing have increased their operations since the beginning of the year as part of a campaign to exacerbate inter-communal tensions.
A car bomb exploded in the mainly Sunni district of Binoog in north Baghdad, killing at least four people. Throughout Thursday, five other bombs killed ten people in mainly Shi'ite and Sunni districts across the capital, police said.
A further seven people, including three policemen, were killed in clashes between gunmen and security forces in the northern city of Mosul, officials said.
The surge in violence began in April when Iraqi forces raided a Sunni protest camp in the northern town of Hawija, angering Sunni leaders and triggering clashes that spread across the country.
More than 1 100 people have been killed since then, raising the risk of a relapse into outright sectarian warfare like that which killed thousands of people in 2006-2007.
Security officials blame Sunni Islamists and al-Qaeda's local wing, the Islamic State of Iraq, for most of the violence.
Thousands of Sunnis have protested weekly in the streets in western provinces since December, and the country's government - split among Shi'ite, Sunni and ethnic Kurds - is caught up in disputes over how to share power.
Many Sunnis accuse Prime Minister Nouri al-Maliki, a Shi'ite, of sidelining their sect to shore up Shi'ite power. Shi'ite leaders counter that many Sunni leaders are working to scuttle power-sharing agreements.
Attempts to defuse the political crisis have been hampered by deep divisions within the Sunni political leadership where moderates who favour negotiations have sometimes been targeted by hardliners who want Maliki to step down.
The Sunni governors of Anbar and Salahuddin provinces both escaped assassination attempts on Thursday when their convoys were targeted by car bombs. Both men, who were unhurt, have been co-operating with Maliki to try to overcome Sunni discontent.