The threats were primarily direct against companies that are moving into Anbar province in northern Iraq, one of the main battlegrounds of the Iraqi insurgency in 2004-08.
The sheiks are bitter because they fear that in corruption-riddled Iraq, the unruly region will see little benefit from the development of the gas fields by the Baghdad government.
"We will not help the companies and the population could even create trouble preventing companies from working if the gas is not used to feed electricity stations and give work to residents," declared prominent Anbar businessman Muhkles Ibrahim who lives in Qaim near the Syrian border.
On Oct. 20, Iraq's Oil Ministry awarded production contracts to foreign companies to develop three of its biggest gas fields. The two biggest -- Akkaz in Anbar and Mansouriya in Diyala province -- lie in regions where insurgents are still active.
A consortium comprising the Korean Gas Corp. of South Korea, or Kogas, and KazMunaiGaz of Kazakhstan got Akkaz, which sprawls across an area 31 miles by 11 miles and contains an estimated 5.6 trillion cubic feet of natural gas.
"If the companies come to invest in Akkaz they must cooperate and serve the people of the region," cautioned Nawaf Ghadas, another business leader in Qaim.
The Mansouriya field will be operated by a consortium of the Turkish Petroleum International Co., Kogas and Kuwait Energy. It contains around 4.5 trillion cubic feet of gas.
The threat of a backlash against the foreign companies, on whom Iraq's hopes of postwar recovery greatly depend, has been given weight by the recent resurgence of al-Qaida in Iraq amid the U.S. pullout.
More than 100,000 troops have already been withdrawn, leaving 50,000 in-country.
Although Iraqi security forces are now taking the lead in combat operations, Americans are still involved in the fighting.
Al-Qaida, which was pushed hard during the U.S. military surge of 2007-08, is still capable of mounting devastating operations and is growing more audacious as U.S. forces shrink.
"Al-Qaida's back from the dead," one analyst commented amid reports the jihadist organization is re-establishing sanctuaries in its former strongholds north and west of Baghdad.
This is an ominous sign and carries the threat of sectarian fighting between the majority Shiites and minority Sunnis.
U.S. officials report that hundreds of Sunni fighters who defected from the insurgency during the surge offensive are rejoining their old comrades because they're disenchanted with the Baghdad government.
Dominated by Shiites, the government has refused to absorb these fighters into the security forces as the Americans promised. Hundreds of Sunnis who joined the so-called Awakening Councils have been arrested by Shiite-dominated security forces in a blatant sectarian crackdown.
Bereft of U.S. support, and angry at the government's failure to provide electricity, jobs and security, they are returning to al-Qaida in droves.
Iraqi Defense Minister Abdul Qader Obeidi acknowledges "there are definite signs of regeneration" by al-Qaida but claims his forces can handle the worsening situation in Anbar and Diyala.
That remains to be seen. There are reports that al-Qaida along with remnants of Saddam Hussein's Baath Party, including army and intelligence veterans, have infiltrated the police and have people in senior command positions.
There are dangers in the Shiite-dominated south as well. This is where two-thirds of Iraq's known oil reserves lie, along with vast quantities of gas.
According to The Nation newspaper published in Abu Dhabi, Shiite criminal gangs in the south are joining forces with the Sunni jihadists and have recently launched attacks that have authorities deeply worried.
The southern oilfields and the two offshore terminals that handle most of Iraq's oil exports make tempting targets.
These new alliances reflect the complexities of the security crisis since they bring together groups that have been bitter enemies. The Sunnis, Islam's dominant sect, considered Shiites to be heretics.
But many Shiites, who bore the brunt of Iraq's eight-year war with Iran in the 1980s, have little affinity with their co-religionists to the east and can be as fiercely anti-Iranian as the Sunnis. They see profit in working with al-Qaida.