An explosion went off near a crowded bus stop Monday evening as people sought rides home, killing at least one person and wounding eight. The evening blast was the second of the day in Kenya's capital, twin assaults that came two days after the U.S. warned of possible terror attacks.

The U.S. warning had implied that the militant Somali group al-Shabab would carry out reprisal attacks in response to Kenyan troops' invasion of Somalia in mid-October. The al-Qaida-linked group promised to unleash terror attacks in Nairobi in retaliation.