A huge manhunt is being carried out in Maine for the US Army reservist suspected of murdering 18 people and injuring 13 others in a mass shooting.

Hundreds of police officers and FBI agents are searching for Robert Card, who is said to be armed and dangerous.

Schools and businesses have closed and people have taken shelter as far as 50 miles (80km) away from the scenes of Wednesday's shootings in Lewiston.

On Thursday night, police raided a property in neighbouring Bowdoin.

Part of the search played out on live TV as police executed warrants in the town, which is around a 20-minute drive from Lewiston.

Over a megaphone, police were heard yelling for Mr Card to surrender and to come out of a house "with your hands up".

After a few hours, police departed the scene.

It is unclear what prompted the search, and an official said police were "simply doing their due diligence by tracking down every lead in an effort to locate and apprehend Card".

Wednesday's bloodshed marked the worst mass shooting in the US this year, according to the Gun Violence Archive, which counts those where four or more people are killed or injured, excluding the gunman.

The mass shooting is considered to be the worst recorded in Maine. One of the US' least populous states, it has high levels of gun ownership but relatively low levels of gun violence. The number of victims nearly matches the state's total homicides for all of 2022.

The shooting prompted the area's representative in the US Congress, Marine Corps veteran Jared Golden, to publicly call for a ban on assault weapons. A moderate Democrat, he previously voted against a ban on Capitol Hill.

"The time has come for me to take responsibility for this failure," said Mr Golden, a Lewiston native. "Which is why I now call on the United States Congress to ban assault rifles like the one used by the sick perpetrator of this mass killing".

The search for Mr Card - which is taking place over land, water and air - has now entered its third day.

The shooting began at a bowling alley in the small town of Lewiston just before 19:00 local time (23:00 GMT) on Wednesday, Maine State Police Col. William Ross said. One woman and six men were killed there.

Within about 10 minutes, gunfire was reported at a nearby restaurant, Schemengees Bar & Grille, where eight more men were fatally shot.

Sixteen injured people were initially transferred to local hospitals, three of whom later died.

Lewiston and three nearby towns have remained under a shelter-in-place notice with the suspect at alrge. Schools as well as most local businesses have closed and many will remain so on Friday.

Beyond a few dog walkers, most people appeared to have stayed at home on Thursday. Police are posted on the streets.

The only bustles of activity were near the two shooting sites and the Central Maine Medical Center.

Dr John Alexander, the chief medical officer there, called the attack "unprecedented" for the small city. He said about 50 medical providers, nurses, respiratory therapists and surgeons answered the call to help treat the victims.

Maine State Police said the suspect had recently reported mental health issues, including "hearing voices and threats to shoot up a military installation in southern Maine".

He had reportedly been admitted to a mental health treatment facility in the summer, after behaving erratically during training at the US Military Academy.

In an interview with NBC News, the suspect's sister-in-law, Katie Card, said that family members had reached out to police and the Army to report he was experiencing an "acute" mental health crisis.

This reportedly included a "manic belief" that voices were saying "horrible" things about him.

"He was just very set in his belief that everyone was against him all of a sudden," Ms Card said.

Police denied earlier reports that he was a firearms instructor, saying there was "no indication he attended advanced weaponry courses".

Maine's Governor Janet Mills, a former Lewiston resident, called it a "dark day" for her state and pledged "to seek full justice for the victims and their families".

The FBI and other federal US law enforcement agencies are aiding local and state police in the manhunt. Neighbouring states are also providing resources and remaining vigilant, as the suspect could have travelled across state lines.

Canadian border officials have also been warned to be on alert for the suspect.

In a Facebook post, Schemengees Bar & Grille wrote: "In a split second your world gets turned upside down for no good reason. We lost great people in this community. How can we make any sense of this."

Just-In-Time Recreation, where the attack first began, posted online: "None of this seems real, but unfortunately it is... There are no words to fix this or make it better."

President Joe Biden ordered flags at the White House and other federal buildings to be lowered to half-mast as a mark of respect for those who died.

He also called on Republican lawmakers in Congress to pass gun safety legislation.

"This is the very least we owe every American who will now bear the scars – physical and mental – of this latest attack," he said.

Speaking at a news conference on Thursday, Maine Senator Susan Collins called for a ban on high-capacity magazines.

"Our hearts are heavy with grief," she told reporters. "This heinous attack, which has robbed the lives of at least 18 Mainers and injured so many more is the worst mass shooting that the state of Maine has ever experienced and could ever imagine."