I had a terrible ant problem. I couldn't use chemicals that could hurt my cats. A professional exterminator, explained that thousands of scout ants search for water or food. When a scout ant finds something, it leaves a scent trail
that the other ants follow. That is how so many can appear in a trail so fast. You need to get rid of any trail an ant has left.
I use a small but powerful hand steam cleaner.
I have not had an overwelming ant problem since I started doing this.As soon as I see an ant
...I blast it with steam and any area where I think it might have walked. First I killed all of the ants with steam...cleaned up the areas were they were....then re-steamed the whole area again to get rid of any scent trail.Be watchful...when a new trail starts...steam the Hell out of the area again.
I got mine from QVC. But home depo & other like Target or WalMart might have them too. I think it was about $40. Worth every penny. I clean my bathroom, kitchen, windows and most of my house with it instead of chemicals.
If you don't want to get a steam cleaner, try pouring lots of hot water on them...then use it to get rid of their trail. That technique is really messy but it works. If you have billions of ants outside of your place...you might need a pro to deal with that, but keep all pets out of harms way.
Good luck... PS...I just re-read your post & realized that you live outside of the US.
You might need to order a steam cleaner online. I would love to know how you get rid of those pesky creatures. Please keep us informed.