Indonesia's anti-corruption agency has arrested the head of the country's upstream oil and gas regulator over allegations of bribery, an official said Wednesday.

Rudi Rubiandini, chair of regulator SKK Migas, was arrested at his home in the capital Jakarta late Tuesday and taken in for questioning over claims of bribery, Corruption Eradication Commission (KPK) spokesman Johan Budi said.

Two other men were also arrested and were being questioned, he said, without giving further details.

Rubiandini, a former deputy energy and mineral resources minister, "is suspected of committing an act of bribery, so we are questioning him. He has not officially been named a suspect yet," Budi told AFP.

The KPK also seized hundreds of thousands of dollars in US bills and documents, Budi said.

Upstream normally refers to the search, recovery and production of crude oil and natural gas, whereas downstream refers to the refining of oil and and sale and distribution of oil and gas products.

The arrests come as concern mounts about Indonesia's energy sector following the introduction of a string of nationalistic policies. Companies, such as US oil giant Chevron, have run into legal problems.

Last month three employees of a local Chevron subsidiary were jailed over a series of corruption allegations. The case spooked foreign investors who have battled fast-changing industry regulations and legal uncertainty in recent years.

Indonesia is one of the world's most corrupt countries. Transparency International last year ranked the country 118th out of 176 countries on its annual index, which rates the least to the most corrupt states.

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