Facebook briefly deleted a prominent Russian opposition journalist’s post about Moscow's possible involvement in the downing of a Malaysian airliner in Ukraine last year but restored it later on May 7, calling the removal a "mistake."

Sergei Parkhomenko said Facebook deleted his May 6 post about a report in the independent newspaper Novaya Gazeta stating that Russian military engineers believe the airliner was hit by a Russian-made surface-to-air BUK missile fired by Ukrainian forces.

He said he was subsequently blocked from using his Facebook account as well.

"I just received an automatic notification from Facebook administrators saying that my post yesterday about the Novaya Gazeta report…has been deleted and my account blocked," Parkhomenko wrote in a post circulated on Facebook by his wife, Varya Gornostayeva, on May 7.

Later in the day, the post was again made available on Facebook, apparently both inside and outside Russia.

Facebook spokeswoman Sally Aldous told RFE/RL that the California-based Internet company "mistakenly" removed the post.

"As our team deal with thousands of reports each day we occasionally make a mistake," Aldous said in emailed comments. "In this case we mistakenly removed a post from Sergei Parkhomenko's page but have now restored it when we were alerted to our mistake. We would like to apologize for any inconvenience caused."

Both Facebook and the U.S.-based social-networking site Twitter in recent years have removed posts and accounts critical of Russian authorities based on claims by Russian state media watchdog Roskomnadzor that they violate domestic laws.

Kremlin critics say these efforts are aimed at stifling free speech on the Internet, a key tool of mobilization for Russia’s so-called "non-systemic" opposition, which operates largely on the margins of country’s tightly controlled mainstream political landscape.

Aldous declined to elaborate on the record what specifically triggered the removal of the post. Facebook bars “hate speech,” which it describes as “content that attacks people based on their actual or perceived race, ethnicity, national origin, religion, sex, gender, sexual orientation, disability or disease.”

Parkhomenko said he believes pro-Russian online activists spammed Facebook with complaints. He denied that his post in any way violated social network’s community standards.

"The post contains no violations of the rules of the Facebook community," Parkhomenko wrote in the post distributed online by his wife. "It contains no propaganda of violence, no insults, nothing that would be ground for blocking Facebook accounts."

It does feature the derogatory term "ukropy," which pro-Russian activists regularly use to ridicule Ukrainians loyal to the Kyiv government. Parkhomenko used the term satirically and inside quotation marks, however, as if it were being spoken by Russian officials.

In his post, Parkhohmenko, an acerbic political analyst and veteran journalist, mocks theories pushed by Russian authorities about why Malaysia Airlines Flight MH17 crashed in eastern Ukraine on July 17, 2014 including that the plane was hit by a missile fired by a Ukrainian fighter jet.

In its May 6 article about the purported report compiled by Russian military engineers, Novaya Gazeta said the report’s conclusions did not prove whether Ukrainian forces or the pro-Moscow rebels they are fighting shot down the airliner.

Each side in the bloody conflict in eastern Ukraine has accused the other of responsibility for bringing down the airliner, killing all 298 people aboard.

Dutch prosecutors leading an international investigation into the tragedy have said that the "leading scenario" in their probe is that MH17 was hit by a BUK missile and that they are testing the theory that it was fired from territory held by separatists in eastern Ukraine.

With reporting by Reuters, meduza.io, and novayagazeta.ru