Alarm wont stop going off

[M-Ster]

I put a new battery on my partners renault megane(migrain) cariolet its a 1997

however as soon as i connect the positive on the battery the alarm sounds tried blippin the key doors lock blip again they unlock but alarm just keeps sounding start the car after bout 10 seconds alarm goes off leave car running and it wont re sound soon as engine is switched off it goes again no key blippin or turning of the key will stop.

Any ideas???