Newspaper headlines: 'Terror crackdown' for web giants and 'Scottish showdown' for PM
The Daily Telegraph is one of several newspapers to lead on the home secretary's anger that security services cannot access encrypted WhatsApp messages.
It has emerged that the phone used by the man behind the Westminster attack, Khalid Masood, had connected to the messaging app two minutes before he struck.
Amber Rudd has summoned WhatsApp - Facebook, which owns it - and other online firms, to what the Telegraph calls "showdown talks" this week about how they can stop terrorists hiding behind the technology.
The Sun says there's also outrage in MI5 and asks: "What side are you on WhatsApp?"
The newspaper quotes a senior government source as saying the company is "putting profits before public safety".
However, The Guardian says critics have questioned the need for new powers to allow the security services to access encrypted messages.
Issues about the practicalities of trying to use UK law against global companies that are largely based in the US have also been raised, the newspaper said.
The Islamic State group has flooded YouTube with violent recruitment videos since the Westminster attack, according to The Times.
It says several films directly refer to the deaths in London in an apparent attempt to capitalise on them.
The paper reports that Google, which owns the site, has failed to block the material, despite it being posted under usernames like "Islamic Caliphate".
Google says it has clear policies against inciting violence and removes such content when made aware of it.
City AM's front page says Prime Minister Theresa May is beginning "Brexit week" with a "Scottish showdown" as she heads to Scotland for talks with Nicola Sturgeon.
Mrs May will meet Ms Sturgeon in what will be a "landmark week for the country", the paper says, as Article 50 is due to be triggered on Wednesday.
The newspaper says the prime minister is expected to reiterate her message that now is not the time for a second referendum on Scottish independence, as she gives a speech stressing the importance of the union.
The front page of the Daily Express highlights research suggesting that nine out of ten local authorities in England will increase council tax from next month to help pay for social care.
The paper's editorial calls the increase "depressingly predictable" and demands severe penalties if the extra revenue doesn't go where it's needed.
The Daily Mail's front page carries allegations of a "cover-up" involving David Cameron's advisors and the Uber online taxi firm.
The paper says the former prime minister and George Osborne allegedly told aides to lobby the then mayor of London, Boris Johnson, to oppose proposed curbs on Uber.
The Mail further claims that Downing Street did not hand over details of the alleged lobbying operation when asked to do so, under a freedom of information request - although they later emerged from Transport for London.
A Downing Street spokesman insists that any suggestion of a cover-up is "categorically untrue".
Pictures of five year-old Bradley Lowery, at the England football international on Sunday, feature in many of the papers.
The Daily Mirror says Bradley, who has terminal cancer, "captured the hearts of England" when he led the team out as the mascot.
In most photos he is with the striker, Jermain Defoe, whom he describes as his "best mate".
And The Sun reports that one local council is counting the cost of not filling in a pothole.
It tells how Scott Nicholas has been awarded £10,000 from Peterborough City Council after the wheel of his Ferrari - and other parts of the vehicle - were damaged by hitting one.
The paper reckons that for about £50 the council could have had the hole filled in.