Australia will deploy more than 100 police and military personnel to aid the Solomon Islands, Prime Minister Scott Morrison said on Thursday, as protesters in the Pacific Island nation defied a curfew to protest for a second consecutive day.

Morrison said Solomon Islands Prime Minister Manasseh Sogavare had requested Australian assistance, which Canberra's national security committee quickly approved.

Australia will send 23 police officers immediately to assist with riot control, Morrison said, with a further 50 personnel to enforce security at critical infrastructure.

Morrison said another 43 military troops will be sent to aid Australian police officers.

"Our purpose here is to provide stability and security to enable the normal constitutional processes, within the Solomon Islands, to be able to deal with the various issues that have arisen," Morrison told reporters in Canberra.

"It is not the Australian government's intention in any way to intervene in the internal affairs of the Solomon Islands, that is for them to resolve."

The deployment of Australian personnel comes amid reports and images shared on social media showing crowds of protesters and burning buildings in the Chinatown district of Honiara.

Many protesters travelled from the most populous province Malaita to the capital because of concern about being overlooked by the national government, according to media reports.

The province opposed a 2019 decision to end diplomatic ties with Taiwan and establish formal links with China, resulting in an independence referendum last year which the national government has dismissed as illegitimate.

The Solomons, the scene of some of the fiercest fighting in the Second World War, experienced major rioting in 2006 following disputed elections, with many Chinese-owned businesses in Honiara burnt and looted.

Sogavare on Wednesday declared a 36-hour lockdown in Honiara after the latest unrest, calling it "another sad and unfortunate event aimed at bringing a democratically elected government down".

The lockdown, which would run until 7 a.m. on Friday, would "allow our law enforcement agencies to fully investigate the perpetrators of today's events and to prevent further lawless destruction," Sogavare said.

The Royal Solomon Islands Police Force (RSIPF) urged people attending schools and businesses around Honiara to stay home to avoid being affected by unrest.

"We want to make sure that our streets, schools and businesses will reopen soon after the lockdown," said RSIPF deputy commissioner Juanita Matanga in a statement.

"I am asking for your cooperation until the situation turns normal."