Man wanted over assault on constable, dog

A man is on the run in Sydney after allegedly assaulting a police dog and its handler.

NSW Police say a constable was patrolling the Sydney CBD with his police dog on Australia Day when he saw a 20-year-old man knock over a pushbike just after midnight (AEDT).

When he walked over to speak to the man, it's alleged a 23-year-old and 21-year-old tried to stop him arresting their friend and a scuffle broke out.

An unknown man then ran into the group, police say, assaulting the constable and lifting his dog into the air by its collar.

Police say the officer was forced to strike the man in the face to get him to drop the dog.

Bystanders helped the officer restrain the 20-year-old, 21-year-old and 23-year-old but the man who had grabbed the dog escaped.

The 21-year-old was released pending further investigation, and the other men were charged with resist or hinder police in the execution of duty.

They were granted bail to appear before Downing Centre Local Court on February 19.

The constable was treated for minor injuries by paramedics.

The dog did not require treatment.