Threatens to add to the turmoil gripping Egypt since July coup that removed Morsi.
Tuesday's move by the Cabinet is latest in push to dismantle organization.
Part of military government's two-pronged strategy for containing opposition.
Group compared military rule to that of Adolf Hitler or Roman emperor Nero.
Mohammed ElBaradei says he is being targeted because of his calls for an inclusive political process.
Foreign minister says Egypt is looking outward, "trying to determine who our friends are."
Closure comes two days after a court ordered the group outlawed and its assets seized.
The ruling opens door for authorities to track down the group's elaborate network of social services.
Phone calls come as authorities are preparing to put Morsi on trial on charges of killing protesters.
Group of activists launched a campaign to urge Abdel-Fattah el-Sissi to run for president.
