Kidnappers have demanded a $500,000 (£380,000) ransom for the safe return of an American woman abducted while visiting a popular safari destination in Uganda.

Security forces in the East African country have launched a search operation in Queen Elizabeth National Park, where the 35-year-old tourist and Congolese guide Jean-Paul Mirenge Remezo were snatched on Tuesday evening.

Initial reports identified the missing woman as Kimberly Sue Endecott or Endicott, although some sources simply named her as Kimberly Sue, from Endicott in New York.

Reuters reports that four gunmen ambushed the safari vehicle during a game drive. Two other tourists, described by police as an “elderly couple”, were not taken nor harmed, adds The Guardian.

“The kidnappers, using the victim’s phone, have demanded $500,000,” a police spokesperson said. “We strongly believe this ransom is the reason behind the kidnap.”

The authorities are focusing their search on an area close to the country’s notoriously porous border with the neighbouring Democratic Republic of Congo. The kidnappers’ identity is not yet known, but Reuters reports that “various illegal groups from Somali Islamists to Congolese-based rebels sometimes operate in Uganda”.

“The Somali Islamist militant group al-Shabaab has carried out attacks in Uganda in the past, but has never been known to kidnap anyone for ransom there,” the news agency adds.

The New York Times reports that Queen Elizabeth National Park is generally regarded as safe for tourists - a message echoed by Ugandan army spokesperson Brigadier Richard Karemire, who called the kidnapping “an isolated incident”.

“The security agencies, including the military, are working together to ensure the tourist and the driver are freed unharmed,” he said.

The US Embassy in Ugandan capital Kampala said US citizens should “exercise caution” in the area.