A court in Oman has sentenced the former managing director of Galfar Engineering & Contracting, Mohammed Ali, to 15 years in jail for five counts of bribery in exchange for contracts from a state-owned oil company, Reuters has reported.

The trial was the second against the former Galfar executive. In January, Ali was sentenced to three years in jail over bribes made to Petroleum Development Oman (PDO).

Ali and two other men convicted this year on bribery charges, a former executive of Galfar and a finance ministry official who had served as head of the tenders committee at PDO, have appealed against the January sentence.

The court sentenced Ali to three years in jail for each of the five counts of bribery and ordered the sentences to run consecutively. Ali was also ordered to pay RO1.77m ($4.6m) in fines.

Oman has launched a series of bribery trials over the past few months as part of a crackdown on corruption in the wake of the political unrest in 2011. Last month, the CEO of state-owned Oman Oil Company, Ahmad al-Wahaibi, was sentenced to a total of 23 years in prison and fined RO5m for accepting bribes.

The Court of First Instance in Muscat also convicted a second defendant in the case, Adel al-Raisi, a former aide to the minister of the now-dissolved economy ministry, of organising a bribe made by a senior official at South Korea-based LGI to Al-Wahaibi, and sentenced him to 10 years imprisonment.

A third defendant, the vice-CEO of LGI, who was named in court as Myung Jao Yoo, was found guilty of paying a bribe to Al-Wahaibi after winning a petrochemical project in Sohar Port in Oman. Myung was jailed for 10 years and fined RO4m.