A Sydney man who allegedly threw petrol on police had his clothes catch fire when he was tasered as officers attempted to arrest him.

Police were called to a house on Regent Street at Riverstone in Sydney's west about 11:15am following reports a man was trying to cut down a power pole with a chainsaw.

The 51-year-old man allegedly threw petrol over the officers who approached him.

When police tried to subdue the man with pepper spray and then taser him, the man's clothing caught on fire. The flames were extinguished by police.

Police photograph a container at the scene where the 51-year-old man allegedly threw petrol on police. ( Fairfax Media: Peter Rae )

Officers said the man then ran inside his home and refused to leave, sparking a one-hour standoff.

Specialist police were deployed to the scene and nearby Riverstone High and public schools were placed into lockdown as a precaution.

The man eventually left the house about 12:15pm and was arrested.

He was taken to Westmead Hospital under police guard for treatment to minor burns and is in a stable condition.

A senior constable was taken to Blacktown Hospital after getting petrol in his eyes, and he is also in a stable condition.

Police said investigations into the incident were continuing and charged are expected to be laid.