Oklahoma prison officials violated the First Amendment when they prevented reporters from viewing portions of the botched execution of a death row inmate earlier this year, two news organizations claim in a federal lawsuit filed Monday.

The lawsuit follows the April 29 death of inmate Clayton Lockett, who writhed, moaned and clenched his teeth before he was pronounced dead about 43 minutes after his execution began. Prison officials had stopped the execution after discovering a problem with an intravenous line that delivered a three-drug lethal injection. Lockett died of a heart attack.

Officials lowered a shade 16 minutes after Lockett's execution started, blocking witnesses' view of the gurney. The Oklahoma Observer and the Guardian US are asking a federal judge to declare that the press be allowed to view an execution in its entirety.

Oklahoma Department of Corrections spokesman Jerry Massie declined to comment on the filing Monday, saying the department doesn't discuss pending litigation.

Officials at the Oklahoma State Penitentiary in McAlester have said Lockett's vein collapsed during the lethal injection process, though a full report on his death hasn't been released.

Monday's lawsuit alleges prison officials used the viewing shade inside the execution chamber to block witnesses' view of the procedure both before and after it was under way.

"The assembled press was denied the opportunity to observe Clayton Lockett entering the execution chamber and his intravenous lines being prepared and inserted," it states. The viewing shade was lifted as Lockett's execution began but prison officials lowered it again in the middle of the procedure, "prematurely terminating press access," according to the lawsuit.

Associated Press writer Sean Murphy, who witnessed the execution, described Lockett writhing against the straps that held him on the gurney and gritting his teeth and moaning. Curtains in the execution chamber were closed about 16 minutes after the injection began. The director of the state's prison system, Robert Patton, later called off the execution, but Lockett died about 10 minutes later.

"Meaningful access to, and oversight of, execution proceedings is critical to the public's and the courts' ability to assess the propriety and lawfulness of the death penalty," the lawsuit states. "The public is deprived of the right to receive information about, and discuss the propriety of, the execution method if it is denied access to critical details of the state's execution proceedings."

ACLU Staff attorney Lee Rowland said the First Amendment guarantees the right of the press to witness executions so the public can be informed about the government's actions and hold it accountable.

"The need for public oversight is as critical at the execution stage as it is during trial," Rowland said in a statement.

"Regardless of where Oklahomans stand on the death penalty, the idea that the government has the right to exercise its ultimate power in secret is one that we can all reject," said Ryan Kiesel, executive director of the ACLU of Oklahoma.

The lawsuit is the second filed in federal court in connection with Lockett's execution. A lawsuit filed in June by 21 Oklahoma death row inmates alleges prison officials are experimenting on death row inmates by changing lethal injection drugs and protocols in violation of the U.S. Constitution's ban on cruel and unusual punishment.