Bern cantonal police were notified about the apparent crime of passion around 7am in Wilderswil near a school and the village's train station, the Berner Zeitung newspaper said online.
The bodies of three people were found outside a residence on the village's main road.
Police, who were continuing to investigate the case late in the afternoon, confirmed that three people died in what they described as a "relationship offence", but otherwise remained tight-lipped.
The Zurich-based Tages-Anzeiger newspaper reported online that the victims, a woman, her former husband and her latest husband, were all Portuguese.
Citing an acquaintance of the female victim, the newspaper said the former husband shot the couple, who were married two months ago, before killing himself.
The paper said the ex-husband also wanted to shoot their three children, aged seven to 18.
The man had reportedly been harassing his former partner for some time in an apparent fit of jealousy.
"She was finally happy again, remarried and with a new job," the woman's supervisor at the laundromat where she worked was quoted as telling the Blick tabloid.
Police arrived at the scene in several patrol cars, along with a couple of ambulances, according to various media reports.
A local resident confirmed to the Jungfrau Zeitung, the local daily, that shots were fired on the main road opposite the school.
Officers investigating the scene cordoned off a wide area around the main road through the village, south of Interlaken, the report said.
Traffic was redirected away from the site.
Police set up a white tent at the scene next to the road.
Blick cited a witness saying one body was found in a car in the parking lot across from the train station while two more bodies were lying in a pool of blood on the ground.
Wilderswil is noted as the base for the Schynige Platte railway, which takes tourists to the 2,076-metre-high Schynige Platte, a mountain offering views of such famous Swiss peaks as the Eiger and Jungfrau.
Village mayor Marianne Lehmann said she was shocked by the shootings.
"It is tragic," Lehmann told the Jungfrau Zeitung.
"The atmosphere here in Wilderswil is bad," she said.
"A sad day."
Police guard cordoned off area near crime scene. Photo: Fabrice Coffrini/AFP