OPEC has canceled accreditation for reporters from three major news organizations to cover a conference in Vienna that will feature the head of BP and the European Union’s top energy official.

“We are very concerned by the prospect of OPEC excluding certain journalists, including from Bloomberg, from next week’s seminar,” Bloomberg News said in a statement. “For the sake of market transparency, we strongly advocate for OPEC to allow journalists from relevant global news outlets to attend.”

Reuters and the Wall Street Journal have also had their accreditations withdrawn, according to people familiar with the situation. Reuters and the WSJ had no immediate comment.

The Organisation of Petroleum Exporting Countries, which together with allies in the wider OPEC+ coalition sets oil production policy for 23 countries, is gathering for a seminar at the state-owned Hofburg palace in Vienna on July 5-6.

It’s the second time that OPEC has excluded the journalists from its meetings in about a month. In May, the group decided against inviting reporters from Bloomberg, Reuters and the Wall Street Journal to a policy meeting on June 3-4, even as other reporters were allowed to attend. The group defended its decision at the time, without explaining it.

“This is our house,” Secretary General Haitham Al Ghais said at a news conference after that meeting.

Late on Tuesday, OPEC’s press office told Bloomberg reporters that next week’s event was invitation only — despite having earlier given accreditation to its reporters to attend. The OPEC press office declined to comment.

Executives including BP Chief Executive Bernard Looney are set to join the seminar, which typically focuses more on the industry and its outlook than specific OPEC policy. European Energy Commissioner Kadri Simson is also attending.

A spokeswoman for BP declined to comment. Asked about the ban, Simson said: “I am attending the OPEC Seminar on 5 July as a speaker on the topic of energy sustainability and have decided to not engage with media present at the conference.”

Austria’s Foreign Ministry said it didn’t have knowledge of the agenda or participation arrangements of specific events hosted by OPEC. “We take this opportunity to highlight that media freedom, including enabling media coverage of political developments, is a cornerstone of any democratic society,” the ministry said by email.

Bloomberg News will still travel to Vienna to cover policymakers and executives, as it did for the meeting earlier this month.