Image copyright Reuters Image caption A vigil was held for the six victims on Sunday

Authorities in the US state of Michigan have charged a taxi driver with six counts of murder after he went on a random shooting spree on Saturday.

Jason Brian Dalton, 45, remained expressionless as the charges were read in court on Monday.

He was arrested over the shootings at three different locations in Kalamazoo, with no apparent links to the victims.

Mr Dalton, a driver for cab-hailing app Uber, was reported to be picking up passengers in between the attacks.

Officials in Kalamazoo said Mr Dalton confessed to the killings.

When given the chance to speak at the court hearing, Mr Dalton said he would "prefer to remain silent". He was denied bail.

Mr Dalton's family released a statement, expressing support for the victims and saying they "intend to co-operate in every way" with police.

The company says it had run a background check on the suspect, and police have confirmed he had no criminal record.

"We just can't figure out the motive," public safety chief Jeffrey Hadley told CNN. "There's nothing that gives us any indication as to why he would do this or what would have triggered this. The victims did not know him; he did not know the victims."

He said the attacks were "completely and totally random". None of the victims - which include two people who were seriously injured - had been passengers of the suspect.

'More to be done'

Four people - Mary Lou Nye, 62, Mary Jo Nye, 60, Barbara Hawthorne, 68 and Dorothy Brown, 74 - were killed outside a restaurant. Two more victims - Tyler Smith, 17, and his father, Richard, 53 - were shot dead outside a car dealership.

Speaking about the killings and the thorny issue of gun control in the US, President Barack Obama said: "I've got to assume that all of you are just as tired as I am of seeing this stuff happen in your states."

He said the hard truth was that America probably lost more people to gun violence over the weekend than in the San Bernardino attack last year that killed 14 people.

"Clearly we are going to need to do more if we're going to keep innocent Americans safe," he said, urging "a common sense" approach to gun control "in a bipartisan way without some of the ideological rhetoric that so often surrounds the issue".

He brought in stricter background checks on firearms buyers in early January as part of a series of measures to tackle gun violence.

Image copyright Kalamazoo Police Image caption Local police released this mugshot of the suspect, 45-year-old local man Jason Dalton

One of the seriously injured in the Kalamazoo attack, a 14-year-old girl, was believed to have been dead for more than hour when she squeezed her mother's hand as doctors were preparing to harvest her organs, police officer Dale Hinz told Michigan Live.

A country prosecutor said the suspect is likely to face multiple counts of first-degree murder and attempted murder when he appears in court on Monday.

They are also investigating whether he took fares between attacks, after a local resident reported a hair-raising ride in Mr Dalton's car shortly before the first incident. Uber also says it is offering the authorities assistance in the case.

The shootings unfolded as follows:

At 17:30 local time (22:30 GMT) : A woman is shot multiple times - reportedly in front of her children - outside a Kalamazoo residential building

: A woman is shot multiple times - reportedly in front of her children - outside a Kalamazoo residential building At about 22:00: Father and son shot and killed outside car dealership. A third person is also wounded

Father and son shot and killed outside car dealership. A third person is also wounded At 22:15: Four killed in car park of the Cracker Barrel restaurant. A girl, 14, gravely wounded

Mr Dalton was arrested in the early hours of Sunday following a police manhunt.

A prayer service was held in honour of the victims at a church in Kalamazoo later on Sunday evening.