A suicide bomber targeting an American military delegation outside a government office in eastern Afghanistan has killed 13 people, including 10 schoolchildren and two international service members, Belfast Telegraph said.

The attack comes as the Taliban and other militants step up bombings and raids on police posts nationwide in a major test of the ability of Afghan soldiers and police to hold ground without international military forces, which are now withdrawing.

General Zelmia Oryakhail, provincial police chief of Paktia province, said the bomber was on a motorcycle and detonated his explosives in Samkani district as American forces passed. He said a local school had just let pupils, who were aged between 10 and 16 years old, out for the day.

The American military delegation had just attended a security briefing at the district administrative office, said district chief Saleh Mohammad Ahsas, who was in the meeting. He said the bomber appeared to have been waiting for them and struck as they left the compound. The blast killed people walking nearby, including the schoolchildren.

As the 2014 withdrawal of most international forces looms, insurgents appear to have intensified their attacks and an assassination campaign against police chiefs and local government officials has continued. Hundreds of Taliban fighters have attempted to take over more territory with attacks on police posts in several parts of the country.