The National party’s headquarters have been burgled, its deputy leader, Paula Bennett, has revealed, with three laptops stolen in the “serious” incident overnight.

The break-in occurred on Sunday night or Monday morning at the party’s Auckland office, Bennett told local media, and the burglar had triggered the office’s alarm system.

Staff who turned up for work on Monday discovered the burglary and alerted police. It was being viewed as “highly suspicious” that only computers were targeted, despite the presence of other items of value.

“We’re still working our way through the details of it, but it looks like three laptops were stolen,” Bennett told the New Zealand Herald.

The details were unclear, but it appeared someone had “just grabbed them [the laptops] and run”.

“From an initial look, it looks like that’s all that was stolen,” Bennett said. “It’s very early yet, but they [police] are taking it seriously.”

Bennett said the laptops had been fully encrypted but it was not a good start to an election year. Whoever had stolen them would not be able to log in or access data on the devices, she had been assured.

A national party spokesperson said “the rest of the premises left untouched or disturbed.”

“We take the security of our staff and information incredibly seriously … the nature of the burglary is also highly suspicious, given that our internal party offices aren’t overly visible from the street, the nature of the items stolen, and that the building itself contained other items of high monetary value.”

Police said they had received notification of the break-in at 9.54am on Monday morning and would “attend the scene today”.