The state government has commenced work to place sandstone blocks under the Kurilpa Bridge on the South Bank side, halting it from being used as a place for homeless people to sleep.

Fences were set up around the site in recent weeks, prompting protests from Brisbane City Council Greens councillor Jonathan Sri.

Sandstone blocks were collected at the Kurilpa Bridge and placed underneath the bridge to prevent rough sleeping.

On Thursday, workmen began placing the sandstone blocks under the bridge, with works expected to continue until mid-December.

Housing Minister Mick de Brenni said the state government was "committed" to providing pathways out of homelessness for people staying under the bridge.