Iraqi forces seek to encircle IS fighters in Tikrit
Iraqi army soldiers and Shia militiamen are seeking to encircle Islamic State fighters in Tikrit, on the third day of a major operation to retake the city.
State-run al-Iraqiya TV said government forces were "advancing" but progress has been slowed by roadside bombs.
Security sources said they had captured villages and oil fields east of the city, and blocked a key IS supply line to neighbouring Diyala province.
The offensive is being overseen at least in part by an Iranian general.
On Tuesday, the top US general said Iran's role in Tikrit could be positive, as long as it did not fuel sectarian tensions.
'Suffocate then pounce'
Some 30,000 soldiers and militiamen from the Popular Mobilisation (al-Hashd al-Shaabi) force, backed by Iraqi jets and helicopters, have advanced gradually since the offensive began on Monday.
On Wednesday, a source in the Samarra Operations Command told the BBC that government forces had taken control of the village of al-Maibdi, on the road between Tikrit and the Kurdish-controlled city of Kirkuk, as well as the nearby Ajil and Alas oilfields. The road was a key supply route for IS between Salahuddin and Diyala provinces, the source said.
Another official told All Iraq News that the villages of Siha and Mazraat al-Rahim, just to the north of Tikrit in al-Alam district, had also been retaken.
However, the soldiers and militiamen have not breached IS defences around Tikrit and al-Dour, a town 19km (12 miles) to the south, which officials say is another stronghold of the jihadist group.
Military officials said on Tuesday that al-Dour had been surrounded and sealed off, but that an assault on the town had not yet been launched.
- The Popular Mobilisation (Hashid Shaabi), comprising dozens of Shia militia, takes a lead role in Iraqi operations against IS
- It was formed by the Shia-led government in June 2014 after the army collapsed in the face of an advance by IS across northern Iraq
- Thousands volunteered to fight after Iraq's most senior Shia cleric, Grand Ayatollah Ali Sistani, called on people to take up arms and defend their country and its holy sites
- Iran provides funding, weapons and military advisers to militia in the Popular Mobilisation, and reportedly controls several of them directly
- The Popular Mobilisation is headed by Jamal Jaafar Mohammed, also known as Abu Mahdi al-Mohandis, a former Badr Organisation commander who is close to Iranian General Qassem Soleimani
- Militiamen have been accused of committing atrocities and acting with impunity. Activists say Sunni Arab civilians have been forced from their homes, kidnapped, and in some cases summarily killed
A senior army commander said the operation was focused on preventing IS from launching more attacks, and cutting supply lines to stop reinforcements and weapons reaching Tikrit.
The next step would be to "surround the towns completely, suffocate them and then pounce," Lt Gen Abdul Amir al-Zaidi told the AFP news agency.
Gen Zaidi said progress along roads into Tikrit had been slowed by sniper fire and roadside bombs planted by IS militants since they seized Saddam Hussein's hometown last June. On one 8km (5-mile) stretch of road, soldiers found about 100 mines and bombs.
Troops taking part in the offensive have so far not received the support of US-led coalition aircraft.
Coalition officials said air strikes had not been requested by the Iraqi authorities, but there are reportedly concerns about the prominent role of Iran and its allied Shia militia.
Iranian General Qasem Soleimani, commander of the Revolutionary Guards' Quds Force, was said on Tuesday to have been directing operations from near the frontline east of Tikrit.
He was seen alongside the leader of the Popular Mobilisation, Abu Mahdi al-Mohandis, and Transport Minister Hadi al-Amiri, who heads the powerful Badr Organisation.
Iranian troops are also reportedly operating artillery, rocket launchers and aerial drones.
Gen Martin Dempsey, chairman of the US Joint Chiefs of Staff, said the Tikrit campaign signalled a new level of Iranian involvement but added that it could turn out to be "a positive thing".
"This is the most overt conduct of Iranian support, in the form of artillery and other things," he said in a response to questions from members of the Senate armed services committee.
"Frankly, it will only be a problem if it results in sectarianism."
The UN warned that the operation had to be conducted "with full respect for fundamental human rights principles and humanitarian law" after militia leaders vowed to seek revenge for the massacre of hundreds of soldiers, most of them Shia, at Camp Speicher near Tikrit in June.