By Nina Trentmann and Stu Woo

Nokia Corp. has chosen an external candidate as its new finance chief, part of a wider management shake-up that comes as the telecommunications company tries to catch up in the race to provide 5G internet.

The Espoo, Finland-based company on Thursday named Marco Wirén chief financial officer, replacing Kristian Pullola, who had been in the role since January 2017.

Mr. Wirén is currently executive vice president of Finnish engineering company Wärtsilä Corp. and president of its energy division. Prior to these roles, he had been CFO at Wärtsilä, at steel company SSAB and at network provider Eltel Networks, Nokia said.

Mr. Wirén is set to join Nokia on Sept. 1, the same day as incoming Chief Executive Pekka Lundmark, the company said. Nokia in March announced it was naming Mr. Lundmark -- head of Finnish energy company Fortum Corp. -- to become its next CEO, replacing Rajeev Suri.

Nokia did not immediately respond to a request for comment.

Both Mr. Suri and Mr. Pullola were longstanding Nokia veterans, and the company's external hires indicate a willingness to transform its culture, said Mark Cash, an equity analyst at Morningstar Research Services LLC.

Nokia in recent years struggled to compete with Sweden's Ericsson AB and industry-leader Huawei Technologies Co., even as the U.S. government took wide-ranging measures to try to cripple the Chinese company.

Ericsson and Huawei last year sold equipment for fast 5G internet that sends wireless signals using a new, concentrated technology. Nokia was late to the game because of delays developing computer chips for its hardware. It now offers a product comparable to that of Ericsson and Huawei, but the new leadership team needs to ensure the company regains lost ground, Mr. Cash said.

"It's a critical time for Nokia as 5G networks are built out, and the timing of these successions fit with the company hitting the reset button on its 5G strategy," he said.

From 2015 to 2019, Nokia's share of revenue in the cellular-infrastructure market fell to 19.2% from 24.4%, according to telecom research firm Dell'Oro Group. In the same period, Ericsson's share rose to 27% from 26.2%, while Huawei's lead grew to 30.7% from 27.5%. Analysts, however, say recent U.S. export restrictions could limit Huawei's access to the computer chips it needs to make 5G equipment.

Nokia in 2015 bought France's Alcatel-Lucent SA in a bid to go beyond its core business of making equipment for wireless carriers to become a serious player in manufacturing hardware for landline cable and internet providers. After the $17.7 billion deal closed in 2016, Nokia spent years restructuring to integrate staff and pare back redundant product lines.

Mr. Wirén is expected to help bring down product development costs, Mr. Cash said.

Dominic Chopping contributed to this article.

Write to Nina Trentmann at Nina.Trentmann@wsj.com and Stu Woo at Stu.Woo@wsj.com