(They) are using a multi-pronged attempt in Karachi.
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Increase ethnic/religious tension in China between the majority and the minority Muslim populations.
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Then use the the measures taken against that minority as means to bully China with human rights arm of the UN and the media to put pressure on the regime.
This is already happening, and Karachi is just another step. Additionally, if the bombing is back to the CIA (whether they were involved or not: obviously AN intelligence agency was) then in addition to the above, they increase the growing tension between the Trump admin and China.
Stay frosty.