ANCHORAGE, Alaska (AP) — Environmental groups filed lawsuits aimed at halting efforts by the Trump administration to open up wide swaths of Alaska's Arctic to oil drilling.

Two separate lawsuits were filed late Monday challenging the Bureau of Land Management's plan to allow drilling on more than 18 million acres of land in the National Petroleum Reserve-Alaska. The legal actions contend the administration is rolling back protections for the ecosystem.

The lawsuits came the same day environmental groups filed legal challenges to the Department of the Interior's opening of the coastal plain of the Arctic National Wildlife Refuge to oil and gas lease sales.

"We're pushing back against the Trump administration's assault on the Arctic and drawing the line," said Rebecca Noblin, an attorney for the law firm EarthJustice, which filed separate lawsuits against drilling plans for both areas on behalf of four environmental groups.

Interior spokesperson Conner Swanson said responsible exploration and development of the National Petroleum Reserve-Alaska is vital to the nation's energy independence and economic security.

"The department's commonsense actions are lawful and based on the best available science, and we will continue to implement President Trump's agenda to create more American jobs, protect the safety of American workers, support domestic energy production and conserve our environment," Swanson said.

In June, the Department of the Interior said it planned to open more than 18 million acres of the reserve — an area the size of Indiana — to oil drilling.

The reserve was set aside by President Warren Harding in 1923 for its potential petroleum value. The entire 23-million-acre site on the western North Slope contains about 8.7 billion barrels of oil, according to the U.S. Geological Survey.

The bureau's documentation is not final, but the environmental groups expect the agency to open 82 percent of the western Arctic to oil and gas drilling, including Teshekpuk Lake, the largest lake in Alaska's Arctic and an important breeding grounds for numerous bird species and caribou.

The other lawsuit against the reserve was filed by Trustees of Alaska on behalf of six environmental groups. They contend the bureau broke the law with a new management plan they see as favorable to oil companies without addressing what impact those activities would have on water, land, wildlife or people who live in the region.

"Clearly this administration will stop at nothing to give away public lands to the oil and gas industry, regardless of the impacts to local communities, wildlife and long-protected areas essential to the health of wildlife and people," said Suzanne Bostrom, an attorney with Trustees for Alaska.

An industry group said such actions by critics are misguided and could keep the nation from embracing its energy potential.

"Especially for Alaska, it represents an opportunity to create jobs and provide a new revenue stream during a time when every state is looking for a boost to their economy," said Lem Smith, vice president of upstream policy at the American Petroleum Institute.Smith.