MOMBASA, Kenya — A 9-year-old boy was killed and several other children were wounded on Sunday when a grenade was hurled into a church in Kenya’s capital, Nairobi, two days after Kenyan forces invaded the last major stronghold of the Shabab militant group in Somalia.

No suspects have been apprehended, but suspicion immediately focused on sympathizers of the Shabab who have attacked several churches and public gathering spots in Kenya in the last year.

Kenyan officials have said they do not believe that the relatively small attacks are the work of the Shabab, whose fighters inside Somalia have been trained in terrorist tactics and have killed hundreds of people there with huge suicide bombs. The Shabab’s supporters in Kenya do not have the skills or supplies to stage large-scale operations and thus turn to less complicated attacks like the one on Sunday.