By Colin Packham

SYDNEY (Reuters) - Voting to elect a new government on the tiny Pacific island of Nauru began on Saturday, with international observers invited to monitor the polls for the first time in more than a decade after criticism over human rights in the world's smallest republic.

The United Nations Special Rapporteur on human rights last year urged Nauru to take action to improve its standing in a range of areas including freedom of expression, the independence of the judiciary and crackdowns on media access.

Nauru's government rejected the majority of the U.N criticism.

There were 67 candidates vying for support from just under 8,000 registered voters for the 19 seats in parliament in Nauru, which lies about 3,000 kilometers (1,800 miles) northeast of Australia.

The island also hosts a controversial detention center housing asylum seekers on behalf of Australia - its biggest foreign aid contributor. Under Australian law, anyone intercepted trying to reach the country by boat is sent for processing offshore.

The detention center houses about 500 people and has been widely criticized by the United Nations and human rights agencies for harsh conditions and reports of systemic child abuse. Many staying there have self-harmed.

Political instability has plagued Nauru, with reports of frequent government crackdown's on dissent.

The election is being monitored by international observers for the first time in 12 years including a team from The Commonwealth led by the former President of Kiribati Anote Tong, the government of Nauru said.

"The success of these elections will depend on every individual playing their part to ensure the process is inclusive, transparent and peaceful," Tong said in a statement.

The Commonwealth observer team is expected to issue a report on the credibility of the elections before July 13.

(Reporting by Colin Packham; Editing by Ed Davies)