New York, New York - Rights groups are suing the Trump administration for documentation on its legal justification for the US military's string of deadly boat strikes in the Caribbean and eastern Pacific.

The American Civil Liberties Union, the Center for Constitutional Rights, and the New York Civil Liberties Union filed the lawsuit on Tuesday in the US District Court for the Southern District of New York.

The groups are aiming to force the disclosure of a legal opinion by the Department of Justice's Office of Legal Counsel which apparently claims the US in "armed conflict" with "drug cartels" and suggests the ongoing strikes are lawful acts.

The memo reportedly seeks to shield any US personnel who authorized or participated in the strikes from future criminal prosecution.

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The organizations note in a press release that the US could not be in armed conflict with Latin American drug cartels, which do not meet the necessary criteria to be considered a "non-state actor" under international law.

In absence of those conditions, the groups suggest the Trump administration has engaged in outright murder.

"The public deserves to know how our government is justifying the cold-blooded murder of civilians as lawful and why it believes it can hand out get-out-of-jail-free cards to people committing these crimes," Jeffrey Stein, staff attorney with the ACLU's National Security Project, said in a statement.

"The Trump administration must stop these illegal and immoral strikes, and officials who have carried them out must be held accountable," he added.

Since September 2, the Trump administration has conducted at least 22 strikes on boats in the Caribbean and eastern Pacific, killing at least 87 people.

Trump administration officials have said the strikes are targeting people trafficking drugs, without providing any evidence to support those claims.

Family members insist some of those killed were fishermen, and rights groups say the strikes are illegal even if those targeted were, in fact, ferrying drugs.

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UN Human Rights chief Volker Turk has urged Washington to investigate the strikes' legality, saying there is "strong evidence" they constitute extrajudicial killings.

The Center for Constitutional Rights and the American Civil Liberties Union filed a Freedom of Information Act request in October seeking the OLC memo and other related documents concerning the lethal boat strikes. The Trump administration has so far not released any of the records.

"The Trump administration is displacing the fundamental mandates of international law with the phony wartime rhetoric of a basic autocrat," said Baher Azmy, legal director of the Center for Constitutional Rights.

"If the OLC opinion seeks to dress up legalese in order to provide cover for the obvious illegality of these serial homicides, the public needs to see this analysis and ultimately hold accountable all those who facilitate murder in the United States' name."