"After contacts between the US embassy and Säpo (Swedish Security Service, Säkerhetspolisen), it is confirmed that the American embassy took suveillance precautions of the same kind as those recently discovered in Norway," Ask said at a press conference on Saturday.
"The information we have at our disposal is that this programme mainly concerned search activities aimed to protect the embassy," Ask added.
She said she was not aware of the breadth of the information subsequently gathered beyond the fact it included photos and personal data.
Late on Saturday, the US embassy in Stockholm admitted that it, like other US embassies, has a programme to detect suspicious activities around its facilities as part of normal security precautions to ensure the safety of staff and guests, but challenged the initial claims made in Norway.
"We regret that inflammatory and inaccurate press reporting which began in Norway about this program has caused unease and concern among some of our friends. The embassy's Surveillance Detection Unit (SDU) is exactly what its title states: a programme designed to detect surveillance against US posts overseas," the embassy wrote in a statement.
"It is not a secret program, nor is it an intelligence program. It emerged from the lessons of such horrific terrorist attacks as the Nairobi and Dar es Salaam embassy bombings in 1998, in which our missions had been under hostile surveillance by the terrorists for some time before the attacks. Unfortunately, this surveillance was not detected," it continued.
"As we have learned from recent events throughout Europe, including Scandinavia, no nation is immune from terrorist threats," it added.
The embassy added that it fully respects Swedish law and welcomes Ask's remarks at her press conference, emphasising that it stands ready to answer any questions the Swedish government may have about the programme.
On Wednesday, Norway's TV2 reported that the US embassy in Oslo had conducted illegal surveillance on hundreds of Norwegian residents over the past decade. Similar allegations were aired a day later by a Danish commercial broadcaster.
In Norway, US embassy spokesman Timothy Moore told the country's NTB news agency that the embassy's SDU "was not directed against the host country or its inhabitants" and that "its objective is to discover possible suspect activities in the area surrounding the embassy."
However, Norwegian officials said they had not been informed of the embassy's programme.
"There are rules for the kind of personal information one can collect...and the manner they are recorded and the length of the recording," said Bjørn Erik Thon, director of Norway's data protection body, suggesting that in this case, such rules were not applied.
In Denmark, Justice Minister Lars Barfoed insisted in an email to the Politiken daily that he "had no knowledge whatsoever of the United States carrying out illegal activities from the US embassy in this country."
Barfoed has been summoned for a closed parliamentary hearing on the matter within the next two weeks.
In Sweden, "this activity has taken place for a long time, since 2000, and neither the justice ministry, nor the foreign ministry, nor Säpo, nor the Stockholm police appear to have been informed," Ask said.
On Saturday, the Swedish foreign ministry questioned US Ambassador Matthew Barzun on the subject, TT news agency reported. No details were immediately disclosed about the talks.
Ask was not able to say whether the surveillance was illegal in Sweden.
"The public prosecutor is trying to evaluate if this practise conforms with Swedish law. We understand that countries under high threat take measures to reduce the risk of attacks, but these measures must fall within the framework of Swedish law" and Swedish authorities must be informed, Ask said.