Dolly Parton has released a video, telling fans "I'm not dying", a day after her sister asked the public to pray for her, sparking concerns about the US country star's health.

"I know lately everybody thinks that I'm sicker than I am. Do I look sick to you? I'm working hard," the musician said in a video posted on Instagram on Wednesday, which she filmed while shooting commercials for the Grand Ole Opry music venue in Nashville.

The video came after her sister apologised for scaring fans in her initial Facebook post about Parton's health.

Parton, 79, was recently forced to pull out of a Dollywood event after being diagnosed with a kidney stone.

In her video, Parton thanked fans for their prayers, and explained that "I didn't take care of myself" after her husband died earlier this year.

"So I let a lot of things go that I should have been taking care of," she said. "So anyway, when I got around to it, the doctors said 'we need to take care of this' and 'we need to take care of that'. Nothing major, but I did have to cancel some things."

Parton also laughed about an AI photo she had seen, which shows fellow country star Reba McEntire at her death bed.

"We both looked like we need to be buried," she laughed.

"There's a lot of rumours flying around, and I figured if you heard it from me, you'd know that I'm ok," she said.

She ended by assuring fans: "I'm not ready to die yet. I don't think God is through with me, and I ain't done working."

It comes after her sister Freida Parton posted that she "hasn't been feeling her best" and asked fans for their prayers.

But in a second post on Facebook, she clarified: "I want to clear something up. I didn't mean to scare anyone or make it sound so serious when asking for prayers for Dolly.

"She's been a little under the weather, and I simply asked for prayers because I believe so strongly in the power of prayer. It was nothing more than a little sister asking for prayers for her big sister."

In the previous post, her sister said she had been "up all night praying for my sister", who, she said, "hasn't been feeling her best lately".

Freida Parton did, however, ended her message on an upbeat note.

"She's strong, she's loved, and with all the prayers being lifted for her, I know in my heart she's going to be just fine," she wrote. "Godspeed, my sissy Dolly. We all love you!"

Parton had been scheduled to perform six shows at The Colosseum at Caesars Palace in Las Vegas in December.

But she postponed the gigs until September next year, telling fans she needs "a few procedures" to deal with ongoing "health challenges".

Kidney stones are a common ailment, with more than 1 in 10 people affected according to the NHS. Larger kidney stones can cause considerable pain, and can lead to infections and other issues if not treated.

Earlier this year, Parton lost her husband Carl Dean after nearly 60 years of marriage.

She later dedicated a new song, If You Hadn't Been There, to his memory.

The musician is best known for a string of country crossover hits including Coat of Many Colors, I Will Always Love You, 9 To 5 and Jolene.

Her Las Vegas stint would have been her first visit to the Strip since the 1990s, when she performed alongside her Islands In The Stream duet partner, Kenny Rogers.