Gunmen in Uganda who abducted an American tourist and his driver inside a national park close to the border with Democratic Republic of Congo have asked for a ransom of $500,000.
Police identified the American as 35-year-old Kimberly Sue Endecott and her driver Jean Paul.
They said the kidnappers had later used her mobile telephone to demand a ransom of $500,000 (445,000 euros) for the release of the pair.
"The kidnappers, using the victim's phone, have demanded $500,000," police spokeswoman Polly Namaye said a statement. "We strongly believe this ransom is the reason behind the kidnap."
Earlier on Wednesday government spokesman Ofwono Opondo said Ugandan soldiers were hunting the gunmen, who abducted the pair around dusk on Tuesday.
"Four armed men, not yet identified, between 5:00 pm and 7:00 pm (1400-1600GMT), staged an ambush and kidnapped an American tourist with his Ugandan driver near Katoke Gate in the Queen Elizabeth National Park," Opondo said in a statement.
The two have been identified as Kimberly Sue Endecott, 35 and her driver Jean Paul
"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," Opondo added.
"The priority at this point is to locate, rescue and bring them back to safely."
Four other tourists, who were present when the gunmen attacked but were not abducted or physically harmed, managed to raise the alarm from the lodge where they were staying.
"Four tourists, who were left abandoned and unharmed, later contacted the base and were quickly got safely out of any danger," Opondo said.
A police statement said the couple of Martin Julius and wife Barbel were “very safe.”
“We strongly believe the perpetrators and the victims could still be trapped within our search area and we are hopeful that our efforts will lead to their successful recovery,” the police statement added
There are fears that the kidnappers could have crossed with the pair into the DR Congo.
Queen Elizabeth National Park, one of the East African nation's most famous wildlife reserves, runs along the frontier with conflict-wracked regions of DR Congo, bordering its famous Virunga national park, Africa's oldest national park.
Numerous militia groups and armed gangs roam eastern DR Congo. Virunga suspended all tourism activities last year following the kidnapping of two British tourists. The Britons and their driver were freed two days after the attack.
Queen Elizabeth, in southwestern Uganda lies some 150 kilometres (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.