By Josie Cox 

The tumbling price of oil hammered commodity-dependent currencies as well as shares in oil and gas companies Friday, a day after the Organization of the Petroleum Exporting Countries left its output target unchanged, diminishing hope of any imminent respite for the ailing commodity.

In early trade, Brent crude was an additional 1% lower at $71.86 a barrel, its weakest level in four years, having already plummeted nearly 7% on Thursday. It later picked up slightly.

Analysts had estimated OPEC would need to take 1 million to 1.5 million barrels a day off the market to support oil prices, which have fallen by more than 30% since the summer, but its members didn't bow to the market pressure.

Russia's ruble, which this year has also been pummeled by geopolitical tensions and resulting sanctions, hit yet another all-time low against the dollar, while fellow oil-linked currencies such as the Canadian dollar, Norway's krone and Nigeria's naira slipped too.

One dollar now buys more than 49 rubles. It started the year close to 32.

"OPEC yesterday delivered just about the most unfriendly possible response to ruble and oil prices," Tom Levinson, a strategist at Sberbank said.

He added that it was unclear whether Russia's central bank would intervene to curb the currency's slide.

"[That will] be dictated by the bank's judgment of whether "financial stability" is at risk. It is hard to argue that it is not, but the hurdle to ad hoc intervention has proven high to date," Mr. Levinson said.

Barclays economists said they now expect Brent crude to sink below $70 per barrel and the West Texas Intermediate benchmark to fall even further.

"Over the course of the coming months, oil markets will have to find a new equilibrium--a world where demand elasticities are tested, and non-OPEC supply sensitivities, and particularly the pain threshold for U.S. producers becomes better understood," they wrote in a note.

Turkey, a major oil importer, is a bright spot. Aberdeen Asset Management said it is now taking a more favorable view of the country by buying the Turkish lira.

"There can be a shift from oil-exporter countries, we are already witnessing it in Latin America's weaker growth performance. But on a macro scale, lower energy prices should help global growth, and this should have an overall positive impact on emerging markets," said Viktor Szabo, a portfolio manager at the firm, which manages around 322.5 billion pounds ($402 billion) in assets.

Istanbul's main stock exchange rose 1% on Friday.

"Given that Turkey imports more than 90% of its energy needs, low oil prices will have positive implications," said emerging market strategist Piotr Matys at Rabobank.

Shares in major airlines, including easyJet PLC, International Consolidated Airlines--owner of British Airways--and TUI Travel PLC climbed as much as 2.5%, buoyed by the prospect of cheaper fuel. The Stoxx Europe 600 index of travel and leisure stocks rose 1.3%.

"A fall in oil prices means a fall in petrol prices, a fall in transport costs, and should be treated as a tax cut for consumers," Peter Dragicevich, a strategist at Commonwealth Bank of Australia wrote in a note.

Retail stocks and chemical companies are also widely seen as potential beneficiaries.

But more broadly, the Stoxx Europe 600 index of the region's largest oil and gas companies declined by almost 4% in early trade to a more than one-month low, fiercely underperforming all other sector indexes.

Biggest losers on the pan-European all-share index included BG Group PLC, Petrofac Ltd., Royal Dutch Shell PLC and BP PLC.

London's FTSE 100 index, which has a high exposure to the energy sector, fell 0.3% while Germany's DAX was down 0.1% and France's CAC declined 0.2%. In thin trade following the Thanksgiving holiday on Thursday, the S&P 500 was indicated opening 0.3% lower. Futures, however, don't necessarily reflect moves after the opening bell.

Russia's Micex was down around 0.1% according to Tradeweb, with major oil companies Gazprom OAO and Lukoil OAO two of the biggest fallers. Gazprom bonds were trading lower too.

Write to Josie Cox at josie.cox@wsj.com

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