Will I'tikaaf be Nullified if one Leaves the Masjid to Perform a Janaazah Salah?

Q: It'kaaf-4: When a person in I'tikaaf learnt that the Janaazah salaah was to be performed, he left the Masjid to join in the salaah will the I'tikaaf be nullified and, if so, will it be necessary to repeat it? Is the Janaazah salaah not regarded to be a necessity of the Shari'ah (because of which it is permissible for him to leave the Masjid)?

Answer: Since the Janaazah salaah performed outside the boundaries of a Masjid, the person's I'tikaaf will be nullified and he will have to repeat at least a day's I'tikaaf. If he wishes to, it would be best to repeat all ten days I'tikaaf. The Janaazah salaah is not regarded to be a necessity of the Shari'ah. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.3