The consequences of the January takeover of an Algerian natural gas complex by Islamist militants could be far-reaching because it endangers supply, the International Energy Agency warns.

"A new wave of political unrest in Africa is clouding the outlook of a growing number of producers," the IEA, the West's energy watchdog, in its latest monthly report.

"Following the recent attack on an Algerian gas facility, companies have begun to reassess their security arrangements in the region."

A total of 37 foreign workers were killed in the four-day siege of In Amenas. The closure of the plant, deep in the Sahara Desert of southeastern Algeria near the Libyan border, has cut Algerian production by some 57,000 barrels per day of liquids and 315 billion cubic feet a year, the agency reported.

That in itself isn't necessarily critical in terms of global consumption and cuts in Saudi Arabian oil production, from 10 million bpd in the summer of 2012 to 9.25 million bpd in January, mean that spare production capacity for the Organization of Petroleum Exporting Countries was restored to 4 million bpd for the first time since January 2011.

The 12-member oil cartel includes troubled Algeria and Libya, the main oil and gas producers in North Africa.

But the IEA cautioned that the global market "may be discounting" what otherwise would be seen as a bearish sign "because of the security concerns in North Africa" following the unprecedented scale of the attack on In Amenas by Islamists linked to al-Qaida's North African arm.

Antoine Halff, one of the IEA report's authors, observed, "OPEC is becoming a repository of spare capacity but also a focus of growing security concern lately and this may change market perception of what spare capacity really means."

Algeria normally produces 1.2 million bpd, down from 1.37 million bpd in 2007 and Libya, struggling to recover output after the 2011 civil war, is producing less than the pre-war level of 1.6 million bpd.

More importantly, the continuing lack of security in Libya is scaring off planned multibillion-dollar investment projects.

BP says it's reviewing its long-awaited deep-water gas exploration in the Gulf of Sidra that would give Libyan production an immense boost.

Meantime, Iranian oil production has been steadily slipping because of ever-tightening U.S. and EU sanctions and is likely to slide further. The IEA says it fell 50,000 bpd from December to a 30-year low, with January exports possibly less than 1 million bpd, far below the pre-sanctions level of 3.5 million bpd.

Neighboring Iraq's exports could also be impacted by growing political unrest and a worsening feud between the Baghdad government the Kurdish region over oil and gas rights and revenues.

The failure of Algeria's security forces to protect the In Amenas complex, attacked in apparent response to France's Jan. 11 military intervention against Islamist militants in former colony Mali, caused widespread dismay in the region's energy industry.

"Algerian energy facilities had largely been viewed as immune from this type of violence," noted senior Barclays Bank commodities analyst Helima Croft.

"It's not like the Algerian government was not keenly focused on protecting its energy infrastructure.

"What has been a wake-up call is if it can happen in a place like Algeria, you have to be concerned about facilities across North Africa and the Sahel."

The current fighting in Mali is expected to widen across the region as militants, making a strategic withdrawal in the face of the French-led offensive against them, spread out to launch what is expected to be a regional insurgency that could drag on for years.

Energy facilities are a likely target. Among other factors, these facilities are usually staffed by foreign technicians who could be kidnapped for ransom, a tactic the Islamists have long used to fill their war chests.

"The Middle East and North Africa are the heart of the global energy business, accounting for more than half of global oil reserves," the Financial Times noted.

"Yet the region is increasingly prone to instability as the Arab Spring unleashes passions that have toppled once-entrenched regimes and plunged countries into civil war ...

"But the spread of instability to Algeria," which has avoided the political upheaval of the pro-democracy uprisings that began in Tunisia in January 2011, "is a surprise ...

"Some fear that if Algeria is not safe, nowhere is."