HELSINKI (Reuters) - The former head of Helsinki's drugs squad was sentenced on Friday to three years in jail for official misconduct, aggravated fraud and bribe-taking related to the purchase of police surveillance equipment.

Jari Aarnio was previously sentenced to one year and eight months by a district court, but judges at the Court of Appeal took a harder line, saying his actions were planned and had endangered public trust in the police. He denied the charges.

Such cases are rare in Finland, whose public sector ranks second least corrupt in the world after Denmark.

Aarnio also faces charges, which he denies, of drug dealing and corruption in a separate case that could lead to a sentence of up to 11 years in prison.

In the first case, the court said Aarnio had hidden a financial interest in a company he bought equipment from as the drug squad boss. The surveillance devices were used by Aarnio's unit and also by the Finnish Security Intelligence Service.

The court said in its statement the equipment was not suitable for police use because a member of an organized crime group was also involved in the company.

The case was heard at the appeals court after prosecutors appealed against an initial decision to dismiss the fraud charge. Aarnio had also appealed, asking for all charges to be dropped.

In the separate drug case, Aarnio is suspected of organizing the smuggling of about 900 kg (1,000 lb) of hashish into Finland from the Netherlands, and of preventing police colleagues investigating the case. Sentencing is expected in November.

(Reporting by Tuomas Forsell; Editing by Jussi Rosendahl and Alison Williams)