NAIROBI, Jan. 15 (Xinhua) -- Police and counter terrorist forces are still fighting on Tuesday evening to regain control of a hotel and office complex in the center of Nairobi following an attack at the place.

Inspector-general Joseph Boinnet said the police were still battling the terrorists on Tuesday evening, and had not confirmed the number of those killed, injured or rescued from the scene.

"We are aware that the armed criminals are holding up in the hotel and specialists' forces are currently flashing them out," he said.

A helicopter has been seen flying low at the scene and some Kenyan hospitals are appealing for blood donations.

Foreign embassies in Kenya issued security alerts to their citizens following the terrorist attack, for which Somali militant group al-Shabab claimed responsibility.