11.   Olympics security tightened after airport attack.

12.   Security tightened around U.S. base on Okinawa.

13.   Security tightened, visits limited for Martian meteorite.

14.   Security tightens ahead of funeral of slain opposition leader.

15.   Security tightened as Tamil rebels kill seven.

16.   Security has tightened in the capital with Taliban soldiers stopping vehicles at checkpoints throughout the city.

17.   Security tightened across Fiji as polls open.

18.   Security tightened to avoid attacks on Christians.

19.   Security has been tightening for weeks, with more uniformed federal police in and around the White House complex and packages checked more closely.

20.   Security tightened noticeably Friday at U.S. embassies across West Africa after the State Department temporarily closed six missions because of terrorism fears.