Kabul, Afghanistan (CNN) -- A suicide bomber wearing an Afghan military uniform killed five foreign soldiers at a military base in eastern Afghanistan, the International Security Assistance Force said Saturday.
Four Afghan soldiers were also killed in the attack, a Defense Ministry spokesman said.
The attack happened at Forward Operating Base Gamberi in Laghman Province and was the worst in some time, the ISAF spokesman said.
He added the attack came during a meeting between Afghan soldiers and ISAF mentors.
The suicide bomber was wearing an Afghan National Army uniform when he detonated the explosives. The blast wounded eight more Afghan soldiers and four interpreters.
Taliban spokesman Zabiullah Mojahed claimed 12 foreign soldiers and four Afghan military service members died in the attack. He said the bomber, Abdul Ghani, "joined the Afghan National Army a month ago in order to kill the invaders."
The ISAF spokesman said he was unable to provide further details about the attack and referred requests for more detailed information to the Afghan Ministry of Defense. The Laghman Province base is controlled by the Afghan National Security Forces, the spokesman said.
Gen. Zaher Azimi, a Ministry of Defense spokesman, said he wouldn't comment on the Taliban spokesman's claim.
Journalist Nick Paton Walsh contributed to this report