(Adds NATO soldiers killed)

HERAT, Afghanistan, Sept 6 (Reuters) - A suicide bomber blew himself up in the offices of an Afghan provincial attorney on Saturday killing him, his son and a clerk, the provincial government said.

Separately, two soldiers of the NATO-led force were killed in the east of the country, the alliance said, the latest in a mounting toll of foreign troop casualties.

Violence has surged in Afghanistan this year as the hardline Islamist Taliban have stepped up their campaign of guerrilla attacks backed by suicide and roadside bombs to oust the pro-Western Afghan government and drive out foreign troops.

The attack on the attorney took place in Nimroz, which adjoins the Taliban stronghold of Helmand in the south.

"The suicide bomber managed to enter the compound in Nimroz city and detonated himself killing the attorney and two other people," governor Ghulam Dastagir Azaad said.

He said the suicide attack was the 13th in Nimroz province in the past six months.

The NATO-led International Security Assistance Force, announcing the deaths of two soldiers in the east, did not give their nationalities or the circumstances in which they died.

Foreign troop casualties have mounted in Afghanistan this summer with 43 killed in August, a higher combat toll than in any other month since the U.S.-led invasion in 2001. (Reporting by Sharafuddin Sharafiyaar; Writing by Sanjeev Miglani)

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