A 22-year-old man had been arrested on suspicion of section 18 assault after a "petrol bomb" device was thrown at police officers in Liverpool.

Merseyside Police said the man from Anfield has been taken to a police station to be interviewed.

Inquiries are still ongoing into the incident which happened in Townsend Lane, Anfield, on Tuesday.

Four officers were injured in the attack and required hospital treatment for minor burns.

The incident took place after a warrant was executed shortly before 4pm at an address in Lampeter Road in which a man made his way on to the roof of the nearby Dockers Club in Townsend Lane.

As the officers cordoned off the area in a bid to speak to him and persuade him to come down, they were assaulted.

Officers have been conducting house-to-house inquiries as well as studying CCTV.

It was believed that three officers had been injured but police have since confirmed that a fourth officer was also hurt.

Three were taken to hospital with leg burns and a fourth with facial injuries. They are all hoping to be on duty today.

Merseyside's police commissioner Jane Kennedy condemned the attack as "shocking" and likened the violence to using a gun or knife.

She said: "This shocking attack on police officers who were simply trying to secure the safety of the public is intolerable.

"I regard the throwing of a 'petrol bomb' as being in the same category as shooting a gun or using a knife. All can kill and all can cause serious and sometimes horrific injuries."

She added: "I will do everything in my power to support Merseyside Police in bringing to justice anyone who resorts to such violence, in particular where it is directed against police officers going about their lawful duty."

Assistant Chief Constable Nikki Holland said the incident highlighted the dangers that officers face every day, adding that they put "themselves in harm's way to deal with dangerous situations".

She said: "Police are on the front line every day protecting our communities and this incident serves as a reminder of the very real dangers that police officers face to keep us all safe, day in, day out.

"Acts of violence against our officers such as this will not be tolerated and we will make every effort to bring those people responsible to justice."

A 25-year-old man, from Anfield, has been arrested on suspicion of possession with intent to supply Class A controlled drugs.

Anyone with any information is asked to contact Merseyside Police on 101, or Crimestoppers anonymously on 0800 555 111