This file photo shows a worker looking at a side mirror of a car at the assembly line of General Motors Company in Shanghai. LIU JIN/AFP/Getty Images

General Motors Co on Thursday reported higher-than-expected quarterly earnings, citing strong results in North America and an improved performance in Europe.

The automaker's shares were up 3.5 percent at $33.30 in early trading after rising as high as $33.68. That is still only just above their 2010 initial public offering price of $33, despite three straight quarters of record-breaking pretax profits.

Chief Executive Officer Mary Barra has stepped up efforts to persuade skeptical investors that GM can deliver consistently strong profits - and return billions to shareholders - through the ups and downs of the industry's sales cycles.

First-quarter net income more than doubled to $2 billion, or $1.24 a share.

General Motors Company (GM) | FindTheCompany

Excluding a one-time expense for litigation settlements, earnings were $1.26 a share, well ahead of analysts' expectations of $1.00.

The company said pretax income, excluding one-time items, was a record for the first quarter.

GM said it still expected full-year earnings of $5.25 and $5.75 a share, excluding special items, up from $5.02 in 2015.

Revenue for the first quarter rose 4.5 percent to $37.3 billion. Adjusted profit margins increased to 7.1 percent of revenue from 5.8 percent a year earlier.

North America accounted for 85 per cent of GM's earnings before interest and taxes, reflecting robust profits from sport utility vehicles and pickup trucks.

Margins from the region, however, fell to 8.7 percent from 8.8 percent a year earlier. Chief Financial Officer Chuck Stevens attributed the decline to restructuring costs and more U.S. union members taking packages to retire.

Stevens said the company still expected North American margins of more than 10 percent for 2016.

In Europe, GM broke even, reversing a year-earlier loss of $200 million.

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Stevens affirmed the company's target for 8 percent profit margins in Europe over the next several years, but said the possibility that the United Kingdom will leave the European Union is a concern. "What does that do to pound sterling?" he said. "What does that do to business, and business transactions?"

The automaker narrowed losses in South America. Income from joint ventures in China was flat at $500 million for the quarter.

The Barron’s financial newspaper projected this week the share prices of GM and rival Ford Motor could rise at least 25 percent in the next year, with U.S. auto sales likely to come in stronger than many investors fear.

The stocks of both companies appear cheap, Barron’s said. GM and Ford trade at 5.6 times and 6.6 times expected 2016 earnings, respectively. The broader Standard & Poor’s 500 index has a forward price-to-earnings ratio of 17.

Shares of GM and Ford have been under pressure because of investor fear of a downturn in the U.S. auto market as well as economic weakness in China. But investors are forgetting several positive factors, Barron’s said. For one thing, the automakers are much leaner than in previous years, which could help profitability.

Also, while U.S sales could slip from the first quarter’s pace of 17 million-plus units a year, they are likely to plateau in a range between 16.5 million and 17 million vehicles annually, the publication said. Both companies have said they would at least break even in the event annual sales fell to about 11 million.

Healthcare costs for retired unionized workers are no longer an obligation, Barron’s noted. The costs have been shifted to a trust fund run by the United Auto Workers that the automakers paid billions of dollars to create.

Data from Reuters were used to report this story.