The Sun says a letter left at the scene warned that sports idols and celebrities were on a "death list".
The paper says there will be "a ring of steel" in Brussels for Manchester United's game tonight.
The Mirror says security at all this weekend's premier league games will be "at an all-time high".
The Daily Star adds that other stars including Andy Murray, Lewis Hamilton and Rory McIlroy are increasing their security.
Energy price cap
Theresa May is set to announce a cap on energy bills within weeks, according to the Daily Mail.
The paper says EDF energy has "sparked fury" by putting up its prices for the second time in a few months.
The paper welcomes the prime minister's intervention, arguing "rapacious", "mostly foreign-owned energy giants" have exploited customers once too often.
Caroline Flint, Labour's former shadow energy secretary, calls the energy giants "villains" in the Mirror.
She urges Mrs May to "do the right thing" and calls for a protected tariff and a price cap set by the regulator Ofgem.
EDF blames the price increase on rises in wholesale costs, the Guardian reports, as well as levies imposed by the government to fund discounts for poorer households.
UK companies face being frozen out of European space contracts because of Brexit, the Financial Times reports.
The paper says the European Commission, which is setting out terms for the latest phase of the Galileo satellite navigation system, is demanding the right to cancel existing contracts without penalty if a supplier is no longer based in the EU.
The head of the trade association UKspace, Richard Peckham, tells the paper the EU's caution was not surprising since the UK government had failed to say it even wished to stay in the EU space programmes.
The Mail describes yesterday's talks between the US Secretary of State Rex Tillerson, and his Russian counterpart Sergei Lavrov as "grim-faced".
The paper says relations between the US and Russia "are now as frosty as during the Cold War" after Mr Tillerson talked about a low level of trust between the two countries.
The Times says that, despite Russian anger over Syria, calls for continued co-operation over Afghanistan and North Korea suggest Moscow does not want to cut all links so early in the Trump administration.
Diana memorial garden
Photographs of a new memorial garden, planted to mark 20 years since the death of Princess Diana, feature in most of the papers.
The Telegraph says the White Garden at Kensington Palace includes forget-me-nots given to her by her brother.
Its design was inspired by Diana's image and style, according to the Express.
The Mail calls it a "beautiful living tribute".
Although the garden is not open to the public, the Mirror says visitors can see its "stunning carpet" of tulips and narcissi from a public walkway.
The first Antarctic Biennale received a "cool reception", according to the Times.
The million pound expedition to the Vernadsky Station in Antarctica, saw events including a naked Russian performance artist burying his head and shoulders in the snow and a London-based sitar player perform to a herd of seals.
The paper thinks the festival was "snow joke", saying the creatives involved seemed to have succumbed to a "seriously juvenile outbreak of cabin fever".