A boost in equipment sales propelled Caterpillar's first-quarter profit, as a strong global economy helped support construction and energy industry projects.

The maker of heavy equipment and machinery also greatly increased its outlook for the year, citing an upbeat global markets, better pricing and demand.

In morning trading, Caterpillar shares rose 3.4 percent to $159.24.

Profit for the quarter ended March 31 rose eightfold to $1.67 billion, or $2.74 per share, while revenue surged 31 percent to $12.86 billion. The results topped Wall Street expectations.

Construction equipment sales rose 38 percent during the quarter, while energy and transportation equipment sales rose 26 percent. North America remained the company's biggest market, with its Asia/Pacific region coming in as its next biggest.

Caterpillar increased its full-time workforce by 4.6 percent to 99,700 employees between March of 2017 and 2018 to help meet higher demand.

Looking ahead, the Deerfield, Illinois company boosted its full-year outlook by $2 to a range of $9.75 to $10.75 per share. Construction activity in North America and infrastructure growth in China are key reasons for the increase. On average, analysts surveyed by FactSet forecast annual earnings per share of $9.11.

But, the company warned that the outlook does not factor potential trade restrictions. President Donald Trump has threatened tariffs, particularly aimed at China.