A police officer was punched and knocked unconscious as he responded to a report of underage drinking and Covid rule breaches at a County Tyrone bar.
A second officer was then punched when he tried to detain the suspect at the premises in Fintona on Friday evening.
Police said there were about 150 people present when they entered the premises at about 18:35 BST.
A 17-year-old boy was arrested for assaulting a police officer and disorderly behaviour.
The bar was issued with a warning and £1,000 fine.
“It is completely unacceptable that two of our colleagues were carrying out their duties when they were assaulted in such a nasty way. Such despicable behaviour must never be tolerated,” said Ch Insp Johnston McDowell.
The officer who was knocked unconscious was taken to hospital as a precaution, police confirmed.
Northern Ireland’s Covid-19 lockdown rules were relaxed on Friday, allowing hospitality businesses to operate outdoors.
They are required to provide table service only and must limit numbers at each table.
“Police have been working with partners, including the local council environmental health team, to carry out checks at premises to ensure our community can socialise in a safe environment,” Mr McDowell added.
He said they would continue to speak to licensees to check they are adhering to Covid-19 public health regulations as well as alcohol licensing legislation.
“Our approach continues to centre around the four Es – engage, explain, encourage and, if necessary, enforce.”