The Eiffel tower is lit up with the Belgian flag colours of red, yellow and black on March 22, 2016 in Paris, France / AP

The response echoes that to the Paris attacks late last year, when Facebook offered a French flag filter as a way of expressing sympathy with the victims

Thousands of people are turning their Facebook profile photos black, yellow and red to support the victims of the deadly terror attacks in Belgium.

At least 30 people have died in explosions that hit the Brussels airport and Metro.

People are changing their photos to the Belgian flag as a way of expressing sympathy with the victims of those attacks. The response follows a similar movement after the Paris attacks, when Facebook offered the French flag filter within its own website.

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This time, Facebook isn’t offering an official filter. But adding one is still possible with third-party tools.

The easiest way to change your profile photo is to head to the Rainbow Filter website, which lets you add a huge range of pictures and flags onto the top of your profile photo, including the Belgian one.

Once there, you’ll just need to login and let the site have access to your profile photo. (After this is done, go back into your Facebook settings and remove the permissions that Rainbow Filter requires, just so that you’re safe in future.)

The site will grab your photo and put the filter over it, ready for you to add it to your Facebook, Twitter or other profile photo.

The Rainbow Filter site offers the option to have the site add the picture for you – but that also involves letting it post onto your wall. Far better is to click the option to download the image and upload it yourself, which has the added option of being able to take advantage of Facebook’s time-limited profile photos.

To add it, you can just head to your page and click on your profile photo. Click to change it, add any time limit if you want it, and then your page will be updated.