The Kurdish Regional Government (KRG) has deployed thousands of troops around the disputed oil city of Kirkuk for fear of an attack by Iraqi government army and militia, a senior official said.

"Thousands of heavily armed peshmerga units are now completely in their positions around Kirkuk," a top aide to KRG President Masoud Barzani posted on social media on Friday.

"Their order is to defend at any cost," Hemin Hawrami wrote on Twitter.

According to the AP news agency, as many as 6,000 Kurdish troops have been deployed in the Kirkuk area.

The alert came after the Kurdish authorities accused the Iraqi government of massing forces in readiness for a reported offensive to seize Kurdish-held oil fields around Kirkuk, as tensions soared after a vote for independence last month.

They accused the Popular Mobilisation Forces (PMF) - paramilitary units dominated by Iran-trained Shia militia - of massing fighters in two mainly Shia Turkmen areas south of Kirkuk in a bid to provoke a confrontation.

Sources in Kirkuk also confirmed to Al Jazeera the movement of Iraqi forces on two fronts in Kirkuk, in the south and west of the city.

In some areas, Iraqi forces have moved two to three kilometres from Kurdish peshmerga positions, Al Jazeera's Charles Stratford reported from Erbil.

"Certainly the KRG government is very worried," he said. "Some Kurds describe Kirkuk as their Jerusalem, and they are saying that they are not going to give up this city."

Strategic area

Hawrami urged the international community to intervene and call on Iraqi Prime Minister Haider al-Abadi to "order PMF to pull back if he can or if they listen to him".

"No escalation from our side. Just defend and roll them back if they attack," the senior adviser to Barzani said.

The surge in tensions comes two weeks after Kurdish voters overwhelmingly backed independence in a non-binding referendum that the federal government condemned as illegal.

Polling was held in the three provinces that have long formed an autonomous Kurdish region as well as neighbouring areas, including Kirkuk, that Kurdish forces seized from the Islamic State of the Iraq and the Levant (ISIL, also known as ISIS) group during the fightback against the armed group's 2014 offensive through areas north and west of Baghdad.

Kirkuk province is the location of northern Iraq's main oil fields and, even though far more crude is now pumped from the south, it is bitterly disputed between Baghdad and the Kurds.

While the majority of the population in Kirkuk are Kurds, it also has a significant Arab and Turkmen residents, who feel more secure under the protection of the KRG than the Iraqi central government, Al Jazeera's Stratford said.

He pointed out that many Arabs had voted during the Kurdish referendum and supported the split from Baghdad, but he added that there are also those who are loyal to the central government.

Baghdad continues to reject decades-old Kurdish ambitions to incorporate Kirkuk and other historically Kurdish-majority areas in their autonomous region.