Building a hotel in Ethiopia. Writing contracts between African governments and petroleum producers. Bringing together public and private money to build sewers and roads.

Opportunities for U.S. law firms to consult on projects in African nations are growing, and companies here and abroad are increasingly turning to law firms to help do deals, navigate regulations and develop infrastructure projects, say leaders of the new Africa practice group at Williams Mullen.

The Richmond-based law firm, a top 200 U.S. firm with about 250 attorneys, is one of a handful of major U.S. law firms that have recently created practice groups specifically to chase business in Africa, which they see as the new frontier for U.S. companies to expand and invest because of a growing middle class there. Covington & Burling, the District’s largest law firm, last fall hired Witney Schneidman, a former adviser on African policy to President Bill Clinton and President Obama, to launch its Africa initiative. Greenberg Traurig last year brought on Jude Kearney, a corporate attorney who led Patton Boggs’ international business practice group, to develop Greenberg’s Africa practice.

Williams Mullen formed its Africa group in December under the leadership of veteran lobbyist Singleton McAllister, infrastructure finance lawyer Lloyd Richardson and trade specialist Evelyn Suarez. The trio is based in Washington, where the firm has about 25 lawyers, and their backgrounds represent a snapshot of the kinds of legal work U.S. law firms are seeking in Africa.

McAllister, who chairs the group, is the former lead lawyer of the U.S. Agency for International Development and helped author the law that created the African Development Foundation, a government program that offers grants to groups that help create jobs and raise income levels in Africa. Richardson, a former diplomat, represents developers that build transportation and other infrastructure systems. Suarez specializes in import and export laws, an area of increasing importance as trade and investment between African nations and the rest of the world are poised to grow.

“The continent is becoming a fast-growing economy with a middle class and tons of opportunities for the U.S. and Africa with trade, government relations and infrastructure projects,” McAllister said.

Several African countries — including Sierra Leone, Niger, Ivory Coast, Liberia and Ethi­o­pia — are among the fastest-growing in the world, according to an April report issued by the World Bank. Excluding South Africa, the region’s largest economy, GDP in sub-Saharan countries grew 5.8 percent in 2012, compared to global GDP growth of 2.3 percent.

The Obama administration last month announced an initiative, Power Africa, aimed at expanding access to electricity to 20 million new households in Ethiopia, Ghana, Kenya, Liberia, Nigeria and Tanzania. The initiative will be funded largely by government-backed lenders, but opens the door for law firms — which advise on virtually every part of new infrastructure projects — to pick up new business.

“Energy is the biggest ticket item that connects all of Africa,” said Richardson, who spent a year advising the Kenyan government on infrastructure finance during a year-long sabbatical funded by the Treasury Department. “There is a lot of diversity across Africa, but the one thing they have in common is they’re short on energy.”

Kearney, who leads the Africa group at Greenberg Traurig, has focused his practice on Africa for several years. As growth across the continent became more sustainable, more law firms began taking notice, he said.

“It used to be that New York and Washington firms might focus a bit on Africa, but now firms with any amount of substantial commercial activity, particularly in certain industries, have at least begun to consider Africa as a region of activity,” Kearney said. “If you’re a firm with clients that are internationally active, you’d have to be almost willfully ignoring Africa not to focus on it. The time is now.”

Oil and gas, mining and infrastructure “are all very busy sectors because that level of development is necessary for Africa to reach its full potential,” Kearney said. “So law firms and other service providers who are focused on those sectors, or who have clients focused on those sectors, are rightfully interested in what’s going on in Africa. There is probably more activity in Africa in some of those sectors than any other place in the world right now.”