Burglars have struck Masterton more than 11 times in the last week, in some cases stealing from the bedsides of sleeping homeowners.
The burglaries took place in Michael St, South Rd, Edith St, Sussex St, Jeans St and Keaton St in what police believe could be a cluster of connected crimes.
Senior Sergeant Gordon Crawley said in four cases the burglar had entered unlocked houses at night while the owners were asleep and had stolen small portable items, such as cellphones and cash.
In two of the burglaries, the offender had entered the bedroom and stolen items from the bedside table.
"The concerning aspect of these is the offence has been committed while people are at home and asleep in bed."
Entering homes was a "gross intrusion", he said, and he urged people to always secure their houses.
"It's a very personal crime, burglary, breaking into someone's home, and it's a gross intrusion into their lives. We don't normally get many burglaries like this, most burglaries are committed at properties where no one is there -- to have one where the offender is prepared to sneak around the property while the occupants are there is actually quite concerning."
The homeowners had not been awakened by the burglar, even when the burglar had entered the bedroom, Mr Crawley said.
"The next morning one guy noticed his cellphone was gone because his alarm didn't go off to get him up for work -- he used his cellphone as an alarm, as many people do -- and his alarm hasn't gone and he's looked and his cellphone was gone.
"He had thought he'd heard something in the night but discounted it -- but it was actually a person walking through his house who ultimately stole his cellphone."
Anyone who found an intruder in their home was advised to find a safe place, call police and avoid a confrontation.
In some of the burglaries windows and doors were jemmied open, but this tended to be when people were not at home, Mr Crawley said.
Police were unsure if the burglaries were connected but said they appeared to be "clustered" in similar areas, with Michael St hit four times.
"It could be two or three different people unrelated to each other but it seems we've had a spike in burglaries in the last wee while and these are all residential, as distinct from commercial."
People needed to make sure their homes were secure and report anything suspicious to police, he said.
"Make sure any tools or anything used to effect any entry to your house are locked away. Lock your windows and doors.
"It would be nice to go back to the time of our parents when you could leave your house open and trust that it would be left as you'd like it, but it's not like that anymore, so now you have to secure things."
Anyone with information was asked to contact police on (06) 370 0378 or call Crimestoppers on 0800 555 111.