Apple Inc. has been urged by more than 60 human rights and environmental organizations to publicly oppose the detention of climate activists in Vietnam, an increasingly important nation in its supply chain.

“You have a responsibility to weigh in on the systematic persecution and imprisonment of climate leaders in the country,” the groups, which include 350.org and Global Witness, said in a letter Thursday to Apple’s leadership team and board.

“By not making a public statement on this matter, you risk violating your own environmental and human rights policies,” the letter said. Vietnam has seen about a fourfold increase in companies assembling Apple products over the past decade.

Read More: Apple’s iPhone Supply Chain Splinters Under US-China Tensions

The US and the United Nations have previously criticized Vietnam over the jailing of environmentalists on tax evasion charges, including Hoang Thi Minh Hong, a former Obama Foundation scholar, and Nguy Thi Khanh. Activists argue authorities are using the detentions as part of efforts to limit transparency on the country’s energy transition.

Vietnam’s Ministry of Foreign Affairs did not immediately respond to a request for comment. Apple did not immediately respond to a request for comment outside of usual business hours.

The nation — which relies on fossil fuels for more than half its power generation — in 2022 entered into a $15.5 billion partnership with funders led by the European Union and the UK to help finance its transition away from coal.