At least 20 people have died in ethnic clashes in the southern Pakistani city of Karachi, officials say.

Eyewitnesses said vehicles had been torched in different parts of the city, which is Pakistan's commercial capital and has a history of ethnic violence.

This is cause for concern for two reasons.  The first is that a nation like Pakistan, which is barely maintaining national unity to begin with, can ill afford violence to break out along ethnic lines.  Secondly, this occurred in southern Pakistan well away from the northwest tribal areas where the Taleban have taken refuge.  The article continues:

The Pashtun population has grown further since last year when tens of thousands were displaced by the military operation in the country's north-western tribal areas.

Some polititians have voiced fears of Taleban infiltration of the Pashtun community.

The Taleban has basically created a sanctuary in the tribal areas.  Now it appears that they are successfully bringing their views, along with their violence, throughout Pakistan.  This should be very troubling to the US and it's allies.