Kirkuk: Militants seized the Iraqi city of Tikrit on Wednesday but security forces thwarted an assault on Samarra as a lightning jihadist offensive launched in second city Mosul swept closer to Baghdad.
Since the Islamic State of Iraq and the Levant began its spectacular assault in Mosul late Monday, militants have captured a large swathe of northern and north-central Iraq, prompting as many as half a million people to flee their homes.
The speed with which ISIL and its allies have advanced after their seizure yesterday of Mosul -- a city of two million people -- has sent alarm bells ringing in Western capitals.
It has also triggered a hostage crisis for Ankara, which threatened harsh reprisals if 49 Turks seized by the jihadists at its consulate in the main northern city were harmed in any way.
Tehran and Washington, which despite their many differences have a shared interest in preventing Iraq following neighbouring Syria into all-out civil war, both pledged more aid to Baghdad.
ISIL vowed on Twitter that it would "not stop this series of blessed invasions" that has seen the fall of the whole of Nineveh province in the north and swathes of Kirkuk and Saleheddin provinces further south.
Tikrit -- hometown of executed dictator Saddam Hussein -- was the second provincial capital to fall in as many days as the jihadists and their allies captured a string of mainly Sunni Arab towns where resentment against the Shiite-led government runs deep.
"All of Tikrit is in the hands of the militants," a police colonel said of the Salaheddin provincial capital, which lies half way between Baghdad and Mosul.
Another officer said the militants had freed some 300 inmates from a prison there.
After Tikrit`s fall, the operation spread down the main highway towards Baghdad, with militants battling security forces on the northern outskirts of Samarra, just 110 kilometres from the capital.
State television said security forces responded with air strikes, and residents said the fighting subsided without the militants entering the city.
Militants had already tried to seize the city late last week, and were halted only by a massive deployment of troops, backed by tribal militia and air power.
Samarra is mainly Sunni Arab but is home to a shrine revered by the country`s Shiite majority, whose bombing by Al-Qaeda in 2006 sparked a Shiite-Sunni sectarian conflict that left tens of thousands dead.