Fire breaks out at luxury apartment building under construction

A ritzy apartment building under construction in Sydney's south west went up in flames overnight, with police officers probing whether it was deliberately lit.

About 70 firefighters were called about 8.30pm to the block on the corner of Shepherd and Atkinson Streets in Liverpool, NSW Fire and Rescue Superintendent Norman Buckley said.

The building was unoccupied at the time.

Four storeys of the 16-storey building caught fire, however the damage was only minor, NSW Police said.

Crews got control of the blaze at 11.30pm last night and it was completely extinguished just after midnight.

Witness Hannah Freeman was at Liverpool train station when the blaze broke out.

"The smoke is actually not so bad, the blaze itself is intense by the looks of it," she told 9news.com.au.

"The flames themselves appear to be quite large.  Fire, police and ambulance crews have been heading in that direction for a good hour and a half and it appears that water simply is not able to reach the building.

"It appears that one of the biggest dangers is the crane on the adjacent building catching alight," she added.

Liverpool police are investigating to establish whether the fire was deliberately lit.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000.