Two bombs have exploded in Kenya's capital, killing 10 people and injuring 70. Police say two improvised explosive devices blew up in a market area near downtown Nairobi. One of the bombs damaged a mini-van used for public transportation. The blasts come as several countries, including the U.S. and Britain, warn of an increased risk of terror attacks. The U.S. Embassy in Nairobi has tightened security in recent days, citing "recent threat information." An al-Qaida bombing at the embassy in 1988 killed more than 200 people. The embassy says more than 100 people have been killed in shootings, grenade attacks and small bomb attacks in Kenya over the past 18 months. And Kenyan authorities, with the help of the FBI, recently discovered a huge car bomb that could have caused massive damage. Meanwhile, hundreds of British tourists have been evacuated from a coastal area where Islamic extremists have operated. The British government has urged British citizens to leave Mombasa and nearby beach towns.