FILE PHOTO: The logo of Brazil's state-run Petrobras oil company is seen at its headquarters in Rio de Janeiro, Brazil October 16, 2019. REUTERS/Sergio Moraes/File Photo

By Isabel Teles and Marta Nogueira

SAO PAULO/RIO DE JANEIRO (Reuters) -Brazil's environmental agency Ibama greenlit state-run oil company Petrobras to conduct exploratory research by drilling wells in the Foz do Amazonas region, near the mouth of the Amazon river, the firm said in a statement on Monday.

The drilling is expected to begin immediately and last around five months, Petrobras said, adding that for the moment they will not be producing any oil.

The area, in deep waters off the shore of the Amazonian state of Amapa, is considered Petrobras' most promising oil frontier, sharing geology with nearby Guyana, where Exxon Mobil is developing huge fields.

Petrobras is aiming to obtain more geological information through the exploratory research and assess whether there is oil and gas in the area on a commercial scale, it said.

Observatorio do Clima, a Brazilian network of environmental organizations said in a statement that the license was a "sabotage" to the global climate summit COP30, which Brazil will host next month in the Amazonian city of Belem.

At COP30, Brazil is expected to urge the international community to accelerate the transition away from fossil fuels. However, the contrast between the country's energy policies and its climate leadership ambitions has drawn sharp criticism from environmental advocates.

The network called the decision "disastrous" and said social movements will go to court "to denounce the illegalities and technical flaws in the licensing process, which could render the license null and void."

As part of its bid to drill in the ecologically sensitive region, Petrobras conducted an emergency response test in August to assess its preparedness.

Last month, documents showed that Petrobras had failed one part of the test, and was demanded to resubmit its animal-rescue plan.

In Monday's statement, Petrobras said it had met the requirements established by Ibama, "fully complying with the environmental licensing process."

Brazil's Mines and Energy Minister Alexandre Silveira said in a note that a technical defense was made to ensure that exploration is carried out with environmental responsibility, "within the highest international standards."

Petrobras CEO Magda Chambriard celebrated the granting of the license in a press release, calling it an "achievement for Brazilian society."

"We hope to obtain excellent results in this research and prove the existence of oil in the Brazilian portion of this new global energy frontier," she said.

(Reporting by Isabel Teles in Sao Paulo and Marta Nogueira in Rio de Janeiro; Editing by Sarah Morland, Brendan O'Boyle and Marguerita Choy)