A gunman has opened fire inside a health clinic in the United States and at least one bomb has exploded, leaving several people critically wounded.
Police rushed to the Allina Health Clinic in Buffalo in the state of Minnesota just before 11am local time (5am AEDT) after reports of shots fired.
A male caller from the scene reported there were multiple explosive devices that went off inside the building, emergency dispatch audio reveals, with one officer saying "we see evidence of that".
"Glass shattered all across," an officer said over the radio.
Multiple "improvised explosive devices" were found at the healthcare facility, Minnesota Governor Tim Walz said during a briefing with reporters, but was unable to provide more details.