This claim is all over the news now, but here it is from the original source.
Exclusive: according to an official statement of the Italian airport dated September 17th, the British prime minister “travelled to Perugia over the past few days”. (He aphas visited many times in the past. On this occasion, apparently a long weekend for his son’s baptism)
Official Airport Sources: “Johnson landed in Perugia on Friday 11 September at 2 pm and left on Monday morning”.
Downing Street: “This claim is wrong”
So, either that airport is engaging in massive shit stirring (libel?) or Downing Street is lying and the whole government should resign.