A controversial decision to dissolve Vanuatu's parliament looked set to be challenged in court, as opponents accused the country's embattled prime minister of illegally dodging a Friday vote of no confidence.

Hours before a parliamentary vote that could have brought down Prime Minister Bob Loughman's government, he engineered parliament to be dissolved, triggering elections two years earlier than expected.

The opposition -- backed by 17 members of government -- had backed a vote of no confidence in Loughman, who has led the Pacific island nation since 2020.

Opposition figure Ralph Regenvanu said he would be "challenging this dissolution in court", with an emergency petition expected to come as soon as Monday.

The tussle is likely to spell a period of political tumult in Vanuatu, which has traditionally been more stable than the neighbouring Solomon Islands or Papua New Guinea.

"It's unprecedented" said Tess Newton Cain, a long-time Vanuatu watcher and project lead for the Pacific hub at Griffith University, but "not a constitutional crisis at this stage".

Politics in Vanuatu centres around personal ties and regional politics, rather than ideological parties. Membership of coalitions and even political parties can be fluid.

The decision to dissolve parliament was carried out by recently elected president Nikenike Vurobaravu, a party ally of Loughman, prompting questions about political interference.

Loughman insisted the decision was above board.

"The president exercised powers invested in him by the constitution and as a caretaker Prime Minister of a caretaker government, we welcome the decision," he said.

If the decision is upheld, Vanuatu will face elections within the next 60 days.

Before parliament was dissolved, a general election had not been due to be held on Vanuatu until 2024.

In June, the country announced agreements with Beijing, deepening their economic ties with China, after Loughman met Chinese Foreign Minister Wang Yi in the capital Port Vila.

Pacific nations have come under intense political scrutiny amid China-US tensions, with Beijing seeking to increase its security and trade presence in the region.