Written By Chad Bray. From NYTimes.

The investment company Atlas Mara Co-Nvest, backed by British-American banker and former Barclays CEO Robert E. Diamond Jr., said Friday it had increased its stake in Union Bank of Nigeria in its latest bet on the African financial sector.

The company said that it exercised an option to acquire 20.9 percent of Union Bank from Asset Management Corporation of Nigeria for about $270 million.

Following the transaction, Atlas Mara will own 29.9 percent of the Nigerian bank. The company had previously owned shares through its subsidiary, ADC African Development Corp.

Founded in 1917, Union Bank offers financial services to retail and business customers, primarily in Nigeria. As of June 30, it had about $6.3 billion in assets and about 340 branches throughout Nigeria.

“This is a very significant acquisition for Atlas Mara,” Diamond said in a news release. The deal will give Atlas Mara exposure to what it considers strategic markets in Southern Africa, East Africa and West Africa, he said.

The transaction is subject to regulatory approval.

Union Bank was established as Colonial Bank in 1917 and was acquired by Barclays in 1925. It operated under the Barclays Bank DCO name until the 1970s when it underwent structural and ownership changes.

Atlas Mara was formed in 2013 by Diamond and Ashish J. Thakkar, an entrepreneur whose Mara Group conglomerate has real estate, technology and manufacturing interests in 19 African countries.

The company relisted on the London Stock Exchange in August after it completed its acquisitions of ADC and of ABC Holdings, which operates the African bank BancABC.

Atlas Mara also agreed in May to acquire a majority stake in the commercial arm of the Development Bank of Rwanda.

The company raised about $325 million in 2013. It had aimed for an additional $400 million in its fundraising earlier this year, but came up short. It eventually raised about $300 million.

“We are well on the way to becoming a leading African financial institution that will benefit from, and contribute to, the continued growth of rapidly expanding sub-Saharan Africa,” Thakkar said in a news release.

Shares of Atlas Mara were down slightly to $10.20 in trading in London on Friday morning.

Read more at NYTimes.