Police to investigate string of suspicious grass fires in Acton

Firefighters said four grass fires they battled in Acton on Wednesday afternoon appeared suspicious, just one day after saying the same for three grass fires in Kaleen and another in Tuggeranong.

Crews quickly extinguished one grass fire at the base of Black Mountain shortly before 4pm on Wednesday and fought three more within the following hour, an ESA spokesperson said.

One of the fires spread about 40 metres by 30 metres, temporarily closing one lane on Parkes Way, city bound.

"The cause of the fires appear suspicious and has been handed over to ACT Policing for further investigation," the ESA spokesperson said.

It comes after several fires across Canberra on Tuesday were also believed to be deliberately lit.

Firefighters extinguished a small grass fire, about the length of an Olympic-sized swimming pool, at Kambah Pool Road in Tuggeranong after responding to reports of the blaze about 1pm.

Around two hours later, ACT Fire & Rescue and ACT Rural Fire Service were called to four more grass fires in Kaleen, near Haydon Drive and Ginninderra Drive.

On Wednesday evening, an ACT Policing spokesperson said police would continue investigating the fires lit in Kaleen and Acton.

Meanwhile, hazard reduction burns continued in the ACT, to help protect the suburbs from bushfire by reducing fuel loads and its potential to spread.

An ESA spokesperson warned of possible smoke across Yarralumla from 7pm on Wednesday night, as a result of burns near Mariner Place and Alexandrina Drive.

He said when hazard reduction burns occur, people vulnerable to smoke should avoid spending more time outside than necessary.

"People with asthma, other chronic respiratory and/or chronic cardiac diseases should not perform vigorous exercise and should, if possible, stay inside if affected by the smoke," he said.

"People with asthma in particular should continue their medication and consult their general practitioner if they have any difficulties."

The burns in Yarralumla followed a number of other hazard reduction burns across the city's south earlier on Wednesday and on Tuesday.