Police officers foiled two separate attempts to disrupt the congress. The metropolitan police commander, Ceaser Abanga, was shot in the arm during one of the incidents and has since been treated and discharged.
The firearm used in the shooting has however not been retrieved.
Northern Regional Police Public Relations Officer, Chief Inspector Ebenezer Tetteh told Joy News the suspected shooter is still at large.
Meanwhile, Police in the Eastern Region have served notice they would not entertain any person who attempts to disrupt the smooth conduct of a regional congress of the NPP on Tuesday.
There is concern that violence could break out following disagreements over the conduct of elections at the constituency level.
The regional police command says it would work with the party leadership to ensure only accredited delegates enter the conference venue.
Former NUGS President, Frank Annor Dompreh, who is contesting the position of regional organizer, has told Joy News he has what it takes to help the opposition party secure power in 2012.
Incumbent regional chairman, Yaw Gyekye Amoabeng, is meeting with former president Kufuor and other top guns of the party ahead of tomorrowÃ¢â‚¬â„¢s congress.
He faces stiff competition from Lawyer Kwaku Ansah Asare, former director of the Ghana Law School and one Dr Annor, the incumbent regional treasurer. All the aspirants have pledged to work hard to boost the fortunes of the NPP in the Eastern Region.