An American citizen was killed in an hours-long siege on a Kabul guesthouse late Wednesday, the US embassy in Kabul said.

"We can confirm reports that a US citizen was killed in the attack on a guesthouse in Kabul," embassy spokeswoman Monica Cummings told AFP.

"Our thoughts are with the families of the victims at this time. Out of respect for the families of those killed, we have no further information at this time."