Police have charged two children in relation to a fire in the Pilbara town of Onslow which destroyed the town hall, library and shire offices.

The fire started on Sunday night and caused several million dollars damage.

Two boys aged 10 and 11 have been charged with aggravated burglary, stealing and criminal damage by fire.

They will appear in the Onslow Children's Court.

Police say four other children who are below the criminal age of responsibility have been dealt with in accordance with the Young Offenders Act.