That pushed production from OPEC to more than 32.3 million bpd in June, up 173,000 bpd from the previous month, according to the independent figures. The cartel's total production got a boost of 331,000 bpd from the Republic of Congo, which began reporting as OPEC's 15th member this month.
OPEC, along with Russia and several other producer nations, has been limiting output since January 2017 in order to drain a crude glut that sent oil prices to 12-year lows in 2016. However, output from the participating nations has fallen much more than expected, largely due to production problems in several of the countries.
At a contentious meeting last month, the cartel agreed to increase output in light of falling production in Venezuela and looming U.S. sanctions on Iran, the world's fifth-biggest oil producer. The producers agreed to start raising output beginning in July, but OPEC's latest monthly report shows several began pumping more last month.
Iraq chipped in the second-biggest increase in June, upping its output by 71,500 bpd to about 4.5 million bpd. Baghdad was one of several countries that initially expressed skepticism about lifting OPEC's production caps.
The United Arab Emirates and Kuwait raised output by 35,100 bpd and 27,300 bpd, respectively. The Arab nations are seen as two of only a handful of OPEC members with spare capacity.
The gains were offset by a 254,000-bpd plunge in production from Libya, where an ongoing political rift shut several of the country's oil ports. Output also continued to decline in Angola and Venezuela, dropping by 88,300 bpd and 47,500 bpd, respectively.
Iran also posted a small drop, bringing its output to about 3.8 million bpd. U.S. demands for oil buyers to cut Iranian imports to zero by November have roiled the market in the last two weeks. However, crude prices eased Tuesday after Secretary of State Mike Pompeo signaled some countries could get waivers.