American officials say eight US civilians have been killed in a suicide bomb attack in south-eastern Afghanistan. Although according to the officials, it is not clear how many were injured along with the eight confirmed deaths.

State Department spokesman Ian Kelly said the attack happened at a US military base in Regional Command East at Forward Operating Base Chapman in Khost Province, on the border with Pakistan.

Reports say the bomber was wearing an explosive vest in the attack, some reports suggested the attack happened in the gym at the base.

A spokesman for ISAF, the international Nato force in Afghanistan, said that “no US and no ISAF military personnel were killed or injured” in the incident.

In an earlier report a US defense official and a US embassy employee said the victims were all civilians.

“We mourn the loss of life in this attack, and are withholding further details pending notification of next of kin,” Mr Kelly said.

Khost province is one of the Taliban’s strongholds and has been a favorite target of militants over the past year.

The number of foreign civilians who work along with military reconstruction teams at provincial bases around the country and deployed in Afghanistan has been rising as international efforts there focus increasingly on development and aid.

One of the three core elements of the new US strategy for Afghanistan announced by US President Barack Obama at the beginning of the month was a “civilian surge”.

This has been the deadliest year for foreign troops since the 2001 invasion.