taliban operation against an isis cell. now, that came hours after a blast tore through a crowd gathered outside a mosque in kabul. a number of civilians were killed. clarissa ward has the latest from inside afghanistan. >> reporter: this is the most significant explosion that we have seen here in kabul for quite some time now. certainly since that horrific airport blast at the end of august. we believe that it was targeting senior taliban leadership who were attending the funeral prayers of the group spokesperson's mother. now, we don't know exactly how many taliban leaders may or may not have been killed or injured in that attack. they are being quite tight lipped about that at the scene. journalists who tried to gain access were pushed back ostensibly for security measures. we also don't know yet who is, in fact, responsible. the obvious candidate would certainly be isis-k.