RIO DE JANEIRO, Jan 30 (Reuters) - Brazilian state-run oil company Petrobras has been largely unaffected by tensions in the Red Sea, the company's chief executive said, saying it has only had to reroute one vessel in a move that incurred no extra costs for the company.

Most of Petrobras' clients are far away from the conflict zone, while its imports mainly come from ports outside of that area, Chief Executive Jean Paul Prates told Reuters on Monday.

Petrobras is an exception among major oil companies such as Shell and BP, which have halted shipments through the Red Sea due to attacks on vessels by Iranian-backed Houthi militants in Yemen.

The attacks, targeting a route that accounts for about 15% of the world's shipping traffic, have pushed some shipping firms to reroute vessels, increasing costs and causing delays. (Reporting by Marta Nogueira; writing by Fabio Teixeira; Editing by Leslie Adler)