A Melbourne teenager alleged to have had bomb-making materials pleaded guilty this morning to preparing for a terror act.

The 17-year-old told the Children's Court he was "guilty" of one charge of engaging in an act in preparation for, or planning, a terrorist act, local media reported.

Two other less serious charges against the teen, who cannot be identified, were dropped and he did not apply for bail.

Earlier this year, court documents revealed that police had seized a computer from the boy's home when he was arrested in May.

The computer contained encrypted documents entitled 'Pressure Cooker Backpack Bomb with Switch Detonator' and 'Make a Bomb in the Kitchen of Your Mom'.

The national broadcaster said other items seized during the raid included a pressure cooker and lengths of steel pipes fitted with caps.

The teenager is due to face a directions hearing in a county court on Thursday.

In recent months, Australia's government has shown increasing concern over home-grown extremism, raising the country's terror-alert level to high last year.

Last week, five people, including a 15-year-old boy, were charged in Sydney over a terror plot targeting a government building.

And in October, a civilian police employee was shot in the head by another 15-year-old boy outside police headquarters in western Sydney.

The teen was killed in an exchange of gunfire with officers.