The kidnappers then immediately began negotiating with Palestinian officials for their release on Wednesday, police sources said.
The 25-year-old worker at pro-Palestinian rights group Al Mezan, identified by British media reports as Kate Burton, was showing her visiting parents around the town of Rafah when they were bundled into a car and driven away, residents said.
There was no public claim of responsibility, but police sources said officials were in talks with the kidnappers in the hope of securing the hostages' release by early Thursday.
Palestinian police said the kidnappers' car was spotted heading north.
Gaza has seen a rash of kidnappings since Israel quit the coastal territory in September after 38 years of occupation, a move welcomed internationally as a potential spur to peace,
though it has left the Palestinian Authority struggling for
Foreigners taken hostage have mostly been released within hours, usually for a ransom. The last victims were the Dutch principal of the prestigious American School in Gaza and his Australian deputy, who were briefly held last week.