Three robbers armed with a gun and an axe have stolen cash after threatening patrons and staff at a western Sydney pub.

The trio entered the premises in Lalor Park with their faces covered soon after midnight on Friday, police say.

One was allegedly armed with a gun and another with an axe, which they used to threaten those inside before fleeing with cash in a white van.

Police have established a crime scene and are calling for information from witnesses.

AAP ek/af/jsh SYDNEY, Aug 16 AAP - Three robbers armed with a gun and an axe have stolen cash after threatening patrons and staff at a western Sydney pub.

The trio entered the premises in Lalor Park with their faces covered soon after midnight on Friday, police say.

One was allegedly armed with a gun and another with an axe, which they used to threaten those inside before fleeing with cash in a white van.

Police have established a crime scene and are calling for information from witnesses.