Police arrest 21 over 'Batman' pills

More than 20 people have been arrested following a series of raids across NSW as police battle the emergence of 'Batman' ecstasy pills which have been linked to the death of a Sydney teenager.

The pills are stamped with the Dark Knight logo.

Police on Wednesday arrested 17 people in Cooma, in the state's south, and three others on Sydney's northern beaches after 100 MDMA tablets, 500g of cannabis, four rifles, snakes and a large amount of cash were found during the raids.

A 28-year-old Bankstown man was also arrested and charged with three counts of supply prohibited drug large commercial quantity, supply prohibited drug commercial quantity and supply drug small quantity.

Police earlier said they found thousands of ecstasy tablets in Cooma, including the blue 'Batman' ecstasy tablets.

The drugs seized throughout the operation have an estimated street value of $300,000.

More than 250 drug supply offences were allegedly committed by the group.