RIO DE JANEIRO, June 24 (Reuters) - Partial data on Brazil's oil and natural gas production in May points to an increase in volumes compared to April, reverting a series of five consecutive monthly declines, oil and gas regulator ANP told Reuters.

The month-to-month decline seen throughout the year, according to the agency, occurred due to the closure of production units, scheduled and unscheduled stoppages and operational problems.

Oil companies have also alleged the trend was due to the impacts of a strike at environmental agency Ibama, but ANP said it does not have data to provide on the topic at the moment.

ANP did not explain why production will rise in May. Complete data for May should be published by ANP in early July.

In April, Brazil's oil production totaled 3.19 million barrels of oil per day on average, the lowest volume in 12 months and a drop of 4.8% compared to March, according to data from ANP. In relation to April last year, the ANP recorded at the time an increase of 1.69% in Brazilian oil production. (Reporting by Marta Nogueira, Writing by Fabio Teixeira; Editing by Alistair Bell)