Reference: Fataawa Islaamiyyah – Volume 1, Page 20
Question: Is placing a wreath on the grave of the “unknown soldier” equal to aggrandising the dead “saints” and pious people to the point of worshiping them?
Response: This practice is an innovation and excess in terms of revering the dead, and it is similar to the practice of those who over-revere pious people. It is feared that this practice may lead to building domes above their graves, seeking their blessings, and taking them for gods beside Allaah (Subhaanahu wa Ta’aala). This practice should be stopped lest it lead to Shirk.
And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet ﷺ and his family and his companions.