Two men have been arrested on suspicion of the murder of Pc David Phillips, who was mown down and killed by a driver in a stolen car, Merseyside Police said.
The pair, aged 18 and 30, from the Oxton and Wallasey areas of Wirral, have been taken to police stations on Merseyside where they will be interviewed by detectives.
Officers have also executed four warrants in the Oxton and Wallasey areas as part of the investigation.
Detectives are still urging the public to come forward with information.
Detective Chief Superintendent Paul Richardson, said: “I would like to thank the public for their overwhelming support. Since the investigation was launched yesterday we have been inundated with calls from members of the public and as a result we are following up a number of positive lines of inquiry.
“From the hundreds of supporting and caring comments on social media and media websites yesterday, it is obvious that there is overwhelming support for the police and that the public appreciate the work undertaken by officers like Pc Phillips to keep their communities safe.
“I would like to appeal to any members of the public who have any information which could help us with the investigation to come forward.
“You may not think that the information you have will mean that much, but for us that information could be the vital piece of the jigsaw we need and is essential in helping us to build up a picture in relation to what happened on the night.”