Nine state officials and private sector executives have gone on trial in Oman on charges of taking or offering bribes, in a widening crackdown on corruption in the sultanate's oil industry and related sectors.

Corruption is a politically sensitive issue in Oman, which saw sporadic street protests against graft and unemployment in 2011 as political unrest gripped other Arab countries.

The charges, mostly involving infrastructure projects, were outlined in six trials that opened on Sunday. The nine accused all denied the charges when they appeared at the Court of First Instance in Muscat.

Eight individuals, including former or serving state officials, face similar charges in four other trials that have opened in the past six weeks.

Sunday's hearings were postponed to December 26 after defence lawyers sought time to review evidence presented by the prosecution.-Reuters