Mariott hotel lobby is very popular among Pakistanis and is frequented during Ramadan period.
This is a massive explosion and is being targetted to kill Americans. No terrorist organization has claimed responsibility for this explosion. HOwever, this explosion is viewed by many as a response to American adevnturism in Border region of Pakistan. Clearly this could be done by Al-Qaeda, LET combine with the connivance of ISI (Inter Service Intelligence). Mariott hotel is one of the heavily guarded hotel because many American diplomats stay there. This massive explosion couldn’t be possible without someone from Army or ISI supporting it.

The news is pouring in that this was a Car bomb (suicide attack).