efe-epa(Update 1: Adds details about the operation) Kabul

A group of Taliban fighters has attacked the compound of a United States-funded international aid group in the center of Afghanistan's capital on Wednesday, injuring at least nine people officials said.

The attackers first triggered an explosion and then stormed the compound of the building housing the office of the global development charity, Counterpart International, in the Shahr-e-Naw area of Kabul.

Afghan special forces responded to the explosion and engaged the assailants in a nearly six-hour-long battle that ended with the gunning down of at least two militants, said Nasrat Rahimi, a spokesperson for the Interior Ministry.

In addition, public health ministry spokesman Wahidullah Majroh told EFE that “nine injured persons have been evacuated to hospitals from the Shahr-e-Naw blast".

Basir Mujahid, a spokesman for the Kabul police, told EFE that security forces rescued over 150 employees of the aid group and had them evacuated them to a safe area.

“The clearance operation has been completed and all terrorists were killed," Mujahid said.

The explosion took place around 11.45 am in an area that also houses an office of the country's attorney general and the Hanzala Mosque.

Counterpart International, which has been operating in Afghanistan since 2005, is headquartered in the US city of Arlington, Virginia and is financed by the American government.

It operates in 28 countries around the world with a focus on civic engagement projects and the stated mission of “helping people build better lives and more durable futures," according to its website.

The organization was established in 1965 as the Foundation of the People of the South Pacific by an Australian Marist missionary priest, Father Stanley Hosie, and actress Elizabeth "Betty" Bryant Silverstein.

Zabihullah Mujahid, a spokesman for the Taliban insurgency, claimed responsibility for the attack against the non-profit, which, he said, was “created by USAID and is involved in various destructive activities" in Afghanistan.

The Taliban mouthpiece claimed that Counterpart carried out "a dangerous program called Angel to promote relations between men and women."

He said the group trained workers in the Afghan administration to promote "anti-Islamic ideology and Western culture."

The blast targeting the aid group comes on the third day of the Islamic holy month of Ramadan.

Last month, the Taliban announced the launch of its annual spring offensive with a special focus on capturing Afghanistan's urban areas, as the improving weather allows militants to resume operations after three months of harsh winter.

The spring offensive comes even as Taliban leaders have held several rounds of negotiations with the US in Qatar and the United Arab Emirates with the goal of ending the 18-year old war between the parties that was sparked by the American invasion of Afghanistan in Oct. 2001.

Last week, the Loya Jirga – a grand council of elders, politicians, religious leaders and public figures – called for an immediate ceasefire between the government and the Taliban before Ramadan, Islam's holy month of fasting that began on Monday.

But the Taliban rejected the ceasefire offer, calling the Loya Jirga “a gathering of the invaders' supporters."

The war in Afghanistan is currently undergoing one of its bloodiest phases.

After nearly 18 years of brutal conflict, the Afghan government controls 55 percent of the country's area, while the Taliban control around 11 percent of the territory.

The rest is contested between the warring factions, according to the latest data released by the US Congress' Special Inspector General for the Reconstruction of Afghanistan in Jan.