They made the agreement during the 6th OPEC and non-OPEC Ministerial Meeting held here in the Austrian capital on Tuesday, Xinhua reported.
In view of the underlying uncertainties and their potential impact on the global oil market, the meeting decided to extend the decision on "voluntary production adjustments" for an additional nine months to March 31, 2020, OPEC said in a press release.
"After heavy deliberations, we have come to the unanimous decision that we have to continue with our cooperation and maintain production cuts for another nine months," said Russian Minister of Energy Alexander Novak through an interpreter at the press conference after the meeting.
The ministers also decided to keep the maximum level of the cuts (1.2 million barrels per day) intact in order to maintain stability and avoid the future build-up of inventories, he said.
The energy alliance between OPEC and the so-called OPEC+ partners, including Russia, has been reducing oil output since 2017 in order to prevent prices from dropping sharply amid soaring production in the US, which has surpassed Russia and Saudi Arabia to become the world's top producer.
The OPEC also formally signed with the OPEC+ partners a new charter of cooperation, which Saudi Energy Minister Khalid al-Falih called "one of history's strongest producer partnerships, spanning the entire world, from east to west, and which has committed itself to promoting market stability on an ongoing basis."
Novak said the charter would provide a platform for the participants to hold regular meetings and to "react if necessary" to changing market conditions.
"We do not shape our strategy in response to US actions; we shape our actions in response to what the market does," he said.
OPEC Secretary General Mohammed Barkindo compared the new accord to a marriage "for eternity".
"We are confident that with the course of time, probably by next time we meet, we may have some new members joining the charter," he said.
( With inputs from IANS )