Heartless vandals have broken into a pet shop in Sydney’s west, killing hundreds of exotic fish.

Emergency services were called to Ofishal Pets on the Greater Western Highway at Emu Plains just before 10pm on Monday.

When they arrived the store was alight, with firefighters managing to extinguish the blaze.

But the worst was yet to come.

Police found dozens of fish tanks had been smashed, with hundreds of exotic and tropical fish killed.

One tank alone contained fish worth more than $10,000.