SYDNEY (REUTERS) - The Solomon Islands' most populous province, the source of anti-government protesters who converged on the capital Honiara last week, is unhappy that Australia sent in police and soldiers at the request of the Pacific island nation's prime minister, a provincial political aide told Reuters.

Dozens of buildings were burned down and shops looted in the capital's Chinatown as protests against Prime Minister Manasseh Sogavare turned to rioting in which four people died.

The arrival of 100 Australian police and soldiers on Friday (Nov 26), and a contingent of 50 from Papua New Guinea, to support overwhelmed local police has largely restored calm, but tensions remain high.

Fiji said on Monday it would also send 50 troops on Tuesday.

Many of the protesters were from Malaita province, which has a history of disputes with Guadalcanal province where the national government is based, and which opposed the switch by Mr Sogavare's government in 2019 to formally recognise China instead of Taiwan.

Malaita's Premier Daniel Suidani has banned Chinese companies from the province and accepted development aid from the United States.

A political adviser to Mr Suidani said in an interview on Monday that Mr Suidani was unhappy with the arrival of Australian police and soldiers amid a political crisis.

"Their presence on the ground gives a very strong morale boost to Prime Minister Sogavare and his government. They are here at the invitation of Sogavare - how can you be neutral?" said the adviser, Mr Celsus Talifilu, by phone from Malaita province.

"Malaitans were surprised, we are the last ones standing for democracy in the Solomons. We were thinking Australia would see the stand we were taking," he added.

Australia's Prime Minister Scott Morrison said on Sunday that Canberra wanted to provide a stable environment so the people of the Solomon Islands could resolve the situation peacefully.

"We do not take sides in these differences, nor do we take a position on other countries' choices about their diplomatic relationships," Australia's Foreign Minister Marise Payne told Parliament on Monday.

An Australian naval ship will arrive on Tuesday.

Four government members of the Solomon Islands Parliament resigned at the weekend, including a minister. A no-confidence motion in Mr Sogavare has been filed in Parliament by opposition leader Matthew Wale but cannot be debated for seven days.

Another 10 government MPs would have to resign for the motion to succeed.

A spokesman for Mr Sogavare's office told Reuters in an e-mail on Monday he "will not resign under pressure from political opponents that use violence to remove him".

"The opposition leader has every right to file a motion of no confidence, given the fact that he does not have the numbers to succeed," he added.

Mr Sogavare last week blamed interference by unnamed foreign powers for the protests, and in a speech on Sunday said the rioting caused US$200 million (S$273 million) in damage.

The Royal Solomon Islands Police Force said more than 100 people had been arrested on suspicion of looting and burning buildings.

The violence broke out after protesters from a group called Malaita for Democracy travelled to Honiara and called for Mr Sogavare to address them last Wednesday.

The protest got out of control as anger rose and "opportunists" began rioting and outnumbered police, said Mr Talifilu.

Witnesses said the rioters included young men from Honiara's outskirt settlements which have no running water.

Honiara resident and academic Transform Aqorau said the eruption of violence was caused by multiple issues, including high unemployment, overcrowded housing, tensions over the switch from Taiwan to China, and foreign companies failing to provide local jobs.

"There is huge disparity and a sense of alienation too. People want to be heard," he said.