Struggle for Iraq: In maps
Iraqi government forces are continuing to battle Sunni rebels, led by the jihadist group Islamic State in Iraq and the Levant (Isis).
Isis-led forces took control of a number of cities in Iraq in a rapid advance during the second week of June.ISIS militants in Syria and Iraq
The crisis is the biggest threat to Iraq's stability since the withdrawal of US troops at the end of 2011.
On 29 June Isis said it had created a caliphate, or Islamic state, stretching from Aleppo in Syria to the province of Diyala in Iraq.
Setting up a state governed under strict Islamic law has long been a goal of many jihadists.
Based on a details posted on Twitter earlier this year, the map below shows 16 "wilayats", or provinces, that Isis claims to control or where it claims to have a presence.
The areas where Isis is operating largely match areas where its predecessor, al-Qaeda in Iraq (AQI), was active during the peak of the sectarian insurgency in 2006.
AQI was eventually suppressed through a combination of a surge in US troop numbers and Sunni tribesmen taking up arms to drive it out.
But earlier this month, Isis militants overran Iraq's second largest city, Mosul - after taking the central city of Falluja and parts of nearby Ramadi in December 2013.
Mosul - with its Sunni Arab majority - fell after the collapse of the Iraqi security forces. Although they far outnumbered the Isis fighters, many police and soldiers just abandoned their posts and fled.Ethnic and religious divide
Iraq's Sunnis are increasingly disenchanted with what they see as their systematic marginalisation by the Shia-dominated government in Baghdad and targeting by security forces.Oil source
Iraq is a major source of oil. The Tigris river valley contains a number of key strategic sites, such as the oil refinery at Baiji - the country's largest.
The Baiji plant was shut down on 17 June shortly before Isis launched an attack. The battle has already led to petrol rationing.
Oil experts believe there is no immediate threat to global supplies, because most of the northern oil fields are not in production and most of the big refineries are in the south of the country.
But if Isis were to take Baghdad, the threat to supplies would be far greater.Water and electricity
Haditha Dam is seen as another key strategic target for Isis-led militants. If the dam were captured and destroyed, it would result in serious flooding, as well as disruption to the country's electrical grid and water supply.
Some 2,000 Iraqi troops have been deployed to protect the dam against the advance from Isis forces, from Anah in the north and Jubba to the south.
In January, Isis took control of a dam south of Fallujah and Iraqi forces were only able to re-take it in April.
During their time in control, Isis blocked the Euphrates river flooding the area around Fallujah and cutting off water supplies to southern and central Iraq.Where the main jihadist groups based?
Jihadist groups are spread throughout Africa, the Middle East, and in parts of Asia. Some have connections to al-Qaeda, others do not. But they all share the common goal of creating an Islamist state through violence.
The situation on the ground is dynamic and the location and strength of these groups is constantly changing, as the Isis example shows. These groups often carry out activities outside of the areas shaded on the map below and there are many smaller groups or factions we have not shown, with similar aims.