At least 14 people have been wounded when a grenade was thrown into a nightclub in the Kenyan capital, Nairobi.

The blast early Monday comes a week after Kenya launched a cross-border operation against al-Qaida-linked al-Shabaab militants in southern Somalia, after a wave of kidnappings of foreigners on Kenyan soil.

The U.S. Embassy in Kenya warned Saturday of an imminent terrorist attack in Kenya. The U.S. did not specify who might carry out such an attack, but said the likely targets would include places where foreigners congregate, such as shopping malls and nightclubs.