Military operation in Kirkuk follows 3 weeks of tension since KRG poll

Iraqi forces have launched a major military operation in Kirkuk province, three weeks into a deepening crisis between Baghdad and the country's Kurds since their September 25 independence referendum.

The disputed oil province of Kirkuk took part in the referendum called by Iraqi Kurdish leader Massud Barzani in defiance of Baghdad.

Tensions have escalated between Iraq and its northern autonomous Kurdish region since Kurdish voters overwhelmingly backed independence in the non-binding referendum.

Here are key developments:

- MILLIONS VOTE -
Despite weeks of threats and warnings, the vote goes ahead on September 25 with more than 12,000 polling stations opening for 5.3 million registered voters.

It is held in the three provinces of Iraq's Kurdish region-- Arbil, Sulaimaniyah and Dohuk -- as well as in disputed border areas such as Kirkuk.

Baghdad says the vote is "illegal" and the United States warns it will increase instability.

Neighbouring Turkey warns the Iraqi Kurds they will face sanctions over the referendum vote.

Iran, which has similar fears, announces it will stop all flights to and from Iraqi Kurdistan.

Prime Minister Haider al-Abadi the following day gives authorities in Kurdistan 72 hours to hand the central government control of airports, warning he will otherwise ban international flights to and from Kurdistan.

- A MASSIVE 'YES' -
The official results released on September 27 show that more than 92 percent of voters back statehood. Turnout is over 72 percent.

Barzani says there will be no immediate declaration of independence but calls for negotiations, while Abadi demands the vote be annulled.

- FLIGHTS CUT, SCREWS TIGHTEN -
The Kurdish region's direct air links with the outside world are indefinitely cut on the evening of September 29. Foreigners stream out on the last flights.

Humanitarian, military and diplomatic planes are excluded from the ban.

The United States says the same day that it does not recognise the vote.

On October 2, Iranian and Iraqi forces conduct joint military exercises with tanks and infantry reported around 250 metres (yards) from the border with the Kurdistan region.

Iran bars exports and imports of fuel products to and from Iraqi Kurdistan "until further notice".

An Iraqi court on October 11 orders the arrest of the chairman and two other members of the commission that organised the independence referendum.

- MILITARY OPERATION -
Government forces on October 13 take control of posts in southern Kirkuk abandoned by Kurdish peshmerga fighters who had held them for three years.

Kurdish leaders at a crisis meeting on October 15 reject an ultimatum for the peshmerga to withdraw from Kirkuk and for the referendum result to be annulled.

Iraqi forces on October 16 seize a key military base, an airport and an oil field in a rapid operation against Kurdish fighters in Kirkuk.

A Kurdish health official says at least 10 peshmerga fighters were killed and 27 wounded during fighting overnight, but there is no confirmation of the toll from the Kurdish government.

Thousands of residents are seen fleeing Kurdish districts of Kirkuk city, heading in buses and cars towards Iraq's Kurdish region.