A top U.K. official is targeting WhatsApp, after reports that the terrorist who killed four people used the Facebook-owned messaging app before launching his attack in London this week.

Home Secretary Amber Rudd complained that WhatsApp’s end-to-end encryption system offered terrorists a safe way to communicate, and said government agencies need to be able to peer inside the messaging app.

“We need to make sure that organizations like WhatsApp, and there are plenty of others like that, don’t provide a secret place for terrorists to communicate with each other,” Rudd told the BBC.

“It used to be that people would steam open envelopes or just listen in on phones when they wanted to find out what people were doing, legally, through warranty,” she said “But on this situation we need to make sure that our intelligence services have the ability to get into situations like encrypted WhatsApp.”

In an op-ed published in the U.K.’s Telegraph, Rudd also said the U.K. would need assistance combatting terror from other internet companies and services, including Google, Twitter, and, surprisingly, blogging platform WordPress.

We’ve asked Facebook for comment. UPDATE: Here’s one from a WhatsApp rep: “We are horrified at the attack carried out in London earlier this week and are cooperating with law enforcement as they continue their investigations.”

Rudd’s critique echoes the fight between U.S. law enforcement and Apple after the 2015 terror attack in San Bernardino, California, when the FBI wanted Apple’s help unlocking an iPhone involved in the case.

Asked about Apple during the BBC interview, Rudd said that company also had a responsibility to help government officials look into apps employed by its iPhone owners.

“If I was talking to Tim Cook, I would say to him that this is something completely different,” she said, referring to Apple CEO.

“We’re not saying ‘open up,’ we don’t want to ‘go into the cloud,’ we don’t want to do all sorts of things like that,” she added. “But we do want them to recognize that they have a responsibility to engage with governments, and engage with law enforcement agencies when there is a terrorist situation. We would do it all through the carefully thought-through, legally covered arrangements. But they cannot get away with saying we are a different situation. They are not.”