On the edge of Tibetan towns in this western province, special police officers carrying rifles stand guard behind checkpoints made of sandbags.
Inside the towns, convoys of police vehicles drive up and down the streets. Security personnel stop shoppers and question them.
Six months after Tibetans staged riots and protests against Chinese rule, Beijing still maintains a tight grip on this largely Tibetan area.
Locals say their lives have not yet returned to normal, and many people arrested during the March unrest are still in prison.
'Criminal attacks'