The American woman kidnapped from a national park in southwest Uganda by four gunmen in military uniforms, who are now demanding a ransom of $500,000, has been pictured.

Grandmother Kimberly Sue Endicott, who turns 57 on April 15, was on a game drive in Queen Elizabeth National Park when her vehicle was ambushed on Tuesday evening, according to police.

A friend said Thursday that Endicott had shared an image on Instagram of four armed guards before she suddenly stopped posting two days ago.

Ugandan soldiers on Thursday expanded their hunt for the gunmen, who abducted the California woman and Wild Frontiers Safari driver Jean-Paul Mirenge Remezo, 48, around dusk on Tuesday.

State-run Uganda Wildlife Authority said the Congolese father-of-two was driving without an armed guard despite advice to have one present.

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Kimberly Sue Endicott was kidnapped with Jean-Paul Mirenge Remezo, 48, in Uganda Tuesday

A friend said Thursday that Endicott had shared an image on Instagram of four armed guards and had been posting about her trip

'I know she was planning this trip for a while, because it’s something that she’s always wanted to do,' Endicott's client Pam Lopez told KTLA in a phone interview. 'This was always a big trip she wanted to take.'

Lopez told the station that Endicott - who has a daughter and a granddaughter - has been sharing images on social media from her travels.

Wild Frontiers Safari tour company driver is married father-of-two Jean-Paul Mirenge Remezo. The 48-year-old was born in Congo and grew up near Goma

It was her lifelong dream to go there to see the gorillas.

'She had been posting pictures of her trip up until – it looks like two days ago, which brings it to Tuesday, which I believe is the day she got kidnapped.'

But Lopez admitted she wasn't sure if Endicott's loved ones even knew she had been kidnapped.

She added about the Costa Mesa aesthetician: 'Honestly, I don’t know what to think. I’m still trying to process it.'

Endicott works at Solutions Skincare Studio according to her Facebook profile.

On Thursday teams 'widened the search area' to include the districts of Kanungu and Rukungiri, where approximately 500,000 people live.

'The operation to rescue the tourist is still ongoing,' Uganda's tourism minister, Godfrey Kiwanda, told AFP on Thursday morning.

NTV reported Army spokesman Brigadier Richard Karemire added: 'Let the security forces do their work.'

Between 5pm and 7pm on Tuesday, the tourist and her driver were taken, government spokesman Ofwono Opondo said Wednesday in a statement.

The group was driving through Queen Elizabeth National Park without an armed guard, according to Uganda Wildlife Authority

Martin Julius and his wife Barbel were said to be on a Wild Frontiers Safari tour and alerted a manager when they were abandoned in the ambush

'A joint operation by the Uganda police, Uganda People's Defence Forces (UPDF) and Uganda Wildlife Authority Game Wardens is underway to locate and rescue them.'

Canadian elderly couple Martin Julius and his wife Barbel were left behind on the Edward Track between Katoke Gate the wilderness camp, and reported the kidnapping to the camp manager who came to rescue them.

Deputy Police spokesperson ACP Polly Namaye, said the captors took the keys the van the couple was left in.

They were not abducted or physically harmed. Endecott and the couple entered Uganda on March 29 and flew the next day to the park in the country's southwest, a Uganda Wildlife Authority (UWA) spokesman said.

The safari company's website says Remezo is married, was born in Congo and grew up in the area near Goma. He moved to Uganda in 1992 and joined the company with in 2007 with five years of experience in the tourism industry. He speaks English, Swahili and French.

Police said the initial indications lead them to believe that the kidnapping was financially motivated.

The group quickly made their demand for Shs1.8billion using Endecott’s cellphone.

'We strongly believe this ransom is the reason behind this kidnap,' the police stated Wednesday. 'The Joint Security teams have cut off all exit areas on the border between Uganda and the DRC in search of the victims.'

On Thursday police said the captors were still use devices from the kidnapped people to ask for ransom money.

'They (the abductors) continue to use cell phones of the victims to call the lodge they were staying asking for $500,000 ransom, which we will not offer,' Uganda Deputy Police Spokeswoman Namaye said.

The state-run Uganda Wildlife Authority (UWA) said an armed ranger is supposed to be with tourists and their guides at all times.

'We have armed ranger guides, if you're going out on a drive in the park you're supposed to have one but these tourists went out on their own without a guard,' spokesman Bashir Hangi told Reuters.

'From their camp in the park, they just got into a vehicle and went out. They should have notified us and informed us that they're going out for a game drive and then we would have availed them a guard but they didn't do this.'

Uganda Wildlife Authority spokesman Bashir Hangi (pictured) said: 'They should have notified us and informed us that they're going out for a game drive and then we would have availed them [an armed] guard but they didn't do this'

Queen Elizabeth, in southwestern Uganda lies some 150 kilometers (90 miles) north of Bwindi Impenetrable National Park, famous among tourists for gorilla trekking

Law enforcement believe the group could still be within the park. Joint Security teams have cut off all exit areas on the border between Uganda and the Democratic Republic of Congo

Hangi added to ABC News on Thursday: 'This is a one-off incident, it’s an isolated incident. It is not something that we are known for. We call it an accident. It’s very unfortunate, it is regrettable, but it happened.

'Our parks are very safe right now, tourists are in the parks as I speak. We are known to be a safe country for all visitors. We are known to be a country with people who are warmly welcoming those they don’t know. That’s what we are known for and that’s who we are, and that’s who we are going to remain to be despite this incident.'

But the US embassy in Kampala said to avoid the Ishasha area on Thursday.

On Wednesday it said 'is aware of reports that an American citizen was kidnapped and warned to 'exercise caution when traveling to this area due to ongoing security activity'.

The identity of the kidnappers was unclear. The Somali Islamist militant group al Shabaab has carried out attacks in Uganda in the past, but has never kidnapped anyone for ransom there.

'We are hopeful that our efforts will lead to their successful recovery,' police said, adding they have strengthened safety measures.

'We want to further reassure the public that this is the first incident of its kind registered in such a peaceful setting and those planning to visit the national park and its surrounding should not be discouraged.'

Virunga suspended all tourism activities last year following the kidnapping of two British tourists, Bethan Davies and Robert Jesty, in May 2018

The Britons were freed two days after the attack and their 25-year-old Virunga Park Ranger Rachel Masika Baraka was killed

Queen Elizabeth, in southwestern Uganda lies some 90 miles north of Bwindi Impenetrable National Park, famous among tourists for gorilla trekking.

In 1999, Rwandan rebels killed eight foreign tourists there, inflicting an enormous blow to Uganda's tourist industry.

Queen Elizabeth National Park, one of the East African nation's most famous wildlife reserves, runs along the frontier with conflict-wracked regions of the Democratic Republic of Congo.

It borders its famous Virunga national park, Africa's oldest national park.

Virunga suspended all tourism activities last year following the kidnapping of two British tourists, Bethan Davies and Robert Jesty, in May 2018.

The Britons were freed two days after the attack and their 25-year-old Virunga Park Ranger Rachel Masika Baraka was killed.

Numerous militia groups and armed gangs roam eastern DR Congo.