A suicide bomber slammed a pickup truck packed with explosives into a checkpoint in a neighborhood housing U.N. and international aid group offices in the southern city of Kandahar on Monday, killing five people including the district police chief, Afghan officials said.

The United Nations' refugee agency says three of its employees are among the five people killed in a suicide bombing in the southern Afghan city of Kandahar.

The UNCHR says in a statement that two others were also wounded in the attack early Monday.

Afghan provincial police chief Abdul Razzaq says a suicide bomber drove an explosive-laden pickup truck into a checkpoint near a compound housing U.N. and international aid groups. Three other insurgents then rushed into the compound, sparking an hours-long gun battle with security forces.

All three of the attackers were killed.

The combined bombing and assault was the second major attack in three days to target foreigners or NATO troops in the country, and spotlighted the insurgents' ability to continue to carry out major attacks despite a 10-year NATO campaign against them. The U.S.-led coalition is gradually handing over security responsibilities to its Afghan counterparts and plans to withdraw its combat forces by the end of 2014.

"Despite the insurgency's failures this past year, it remains capable and, enabled by safe havens in Pakistan, continues to contest (Afghan and NATO) progress in some parts of the country," German Brig Gen. Carsten Jacobson, a coalition spokesman in Afghanistan told reporters in Kabul.

But Jacobson also said the coalition and its Afghan partners had made significant gains against the Taliban and that incidents such as the bombing in Kandahar were not indicative of the insurgents strengthening their reach.

"It is not to gain a military victory, it is to gain media" attention he said.

Immediately after the early morning blast, the gunmen seized control of an animal clinic near the office of the International Relief and Development organization, said provincial police spokesman Ghorzang, who like many Afghans goes by one name.

The blast caused extensive damage to the offices of the U.N.'s refugee agency, the UNHCR. Associated Press video footage showed large chunks of the building's outer walls blown out, as well as the windows while the interior was in shambles. The street around the building was strewn with rubble.

The insurgents then managed to enter the IRD's office through the UNHCR building, Ghorzang said.

The Taliban, for whom Kandahar is a traditional stronghold, claimed responsibility for the attack. Spokesman Qari Yousef said the insurgents were targeting what he claimed was a guest house affiliated with the United Nations Assistance Mission in Afghanistan.

The UNAMA does not operate a guest house in the area. However, the clinic and IRD offices entered by the attackers are near guest houses affiliated with both the IRD and the UNHCR. The area is also home to several other international NGO offices and guest houses.

Razzaq, the provincial police chief, said that three civilians and the district police chief, Abdul Aziz Khan, were killed and four people wounded.

UNAMA spokesman Dan McNortan said all of the agency's staff, both Afghan and foreign, was accounted for.

The attack comes two days after the Taliban launched a brazen midday suicide bombing in Kabul, striking a NATO convoy on Saturday and killing 17 people, including five NATO service members, one Canadian soldier and eight civilian contractors.