Pro-Russia separatists in eastern Ukraine should stop threatening and obstructing journalists from reporting on the Malaysia Airlines plane crash, the Committee to Protect Journalists said today.

Since Friday, armed separatists with the self-declared Donetsk People's Republic (DPR) have briefly detained and threatened at least 10 foreign correspondents, according to international press reports and a Ukrainian press freedom group. Journalists in the capital, Kiev, have also told CPJ that DPR separatists are barring Ukrainian journalists' access to the region.

"This is an international tragedy which media from all countries have a right to cover," CPJ Europe and Central Asia Program Coordinator Nina Ognianova said. "We call on those controlling the recovery operation to allow the press to do its job unhindered."

Those held included journalists with the BBC, the Swedish newspaper Dagens Nyheter, the U.S.-based news website The Daily Beast, Time magazine, the Dutch TV broadcaster Nieuwsuur, and the Kremlin-controlled broadcaster Russia Today, the reports said. All of the journalists were released after several hours, reports said.

The journalists had traveled to Donetsk to cover the crash site but were refused entry into the morgue by the separatists, the reports said. They were taken to the Ukrainian national security agency building, which is under DPR control, according to Anna Nemtsova, one of journalists rounded up over the weekend, who wrote of her experience in the Daily Beast.

Nemtsova said the rebels started comparing their knife blades in front of the detained journalists. One of the rebels told them "he had been commanded to grab every journalist showing up at the morgue. Journalists weren't to poke around among the bodies," she wrote.

Some journalists covering eastern Ukraine have taken to Twitter to report being harassed. Kevin Bishop, with the BBC, wrote that he and his crew were detained for three hours, while Rudy Bouma, a journalist with Nieuwsuur, wrote that he was forced to delete his images of Donetsk separatists or "they will shoot our heads off."

Journalists in Kiev told CPJ that Ukrainian journalists' access to separatist-controlled areas, including the crash site, is more restricted than the access granted to foreign journalists.

The local journalists said that separatists require journalists covering the conflict to obtain accreditation from the DPR's self-declared information ministry. But, they said, while foreign correspondents are usually granted permits, Ukrainian journalists are denied access and sometimes detained.

Press freedom conditions in Ukraine, especially in the volatile eastern regions, have steadily deteriorated in recent months, CPJ research shows. At least six journalists or media workers have been killed in Ukraine since violence erupted with the February ousting of former President Viktor Yanukovych, CPJ research shows.

Scores of others, including foreign correspondents, were subject to numerous attacks and detentions.