UNITED NATIONS - UN Secretary-General Ban Ki-moon on Saturday slammed the deadly terrorist attack at a shopping mall in Nairobi, Kenya earlier in the day, calling the act "totally reprehensible."

Ban spoke with Kenyan President Uhuru Kenyatta by phone and extended his condolences to the families of the deceased and the wounded, said a statement from Ban's spokesperson's office.

The death toll in the attack by gunmen at a popular shopping mall in Nairobi has risen to 39. Somalia's militant group Al-Shabaab has claimed responsibility for the attack.

"This premeditated act, targeting defenceless civilians, is totally reprehensible," Ban said, adding that "he trusts that those responsible for this attack will be brought to justice."

In a press statement, UN Security Council members condemned the terrorist attack "in the strongest possible terms" and reiterated their determination to combat all forms of terrorism.