KABUL: Gunmen with automatic weapons and suicide vests stormed a guest house used by U.N. staff in the heart of the Afghan capital early Wednesday, killing at least seven people including three U.N. staff, officials said. A Taliban spokesman claimed responsibility, saying it was meant as an assault on the upcoming presidential election.

Heavy gunfire reverberated through the streets shortly after dawn and a large plume of smoke rose over the city following the attack on the hostel in the Shar-e-Naw district. Kabul police chief Abdul Rahman Rahman said seven people were killed, including some attackers.

U.N. spokesman Adrian Edwards confirmed that three U.N. staff were among the dead and one was seriously wounded. He said 20 U.N. staff were living at the guest house, some of them known to be registered there but he was unsure whether all were there at the time of the attack.

Flames could be seen on the roof of the guest house. Hours after the attack began, three explosions could be heard but it was unclear if they were from that location.

Taliban spokesman Zabiullah Mujahid claimed responsibility for the attack in a telephone call to The Associated Press, saying three militants with suicide vests, grenades and machine guns carried out the assault.

He said three days ago the Taliban issued a statement threatening anyone working on the Nov. 7 runoff election between President Hamid Karzai and Abdullah Abdullah.

"This is our first attack," he said.

Afghans vote Nov. 7 in a second round election after U.N.-backed auditors threw out nearly a third of Karzai's votes from the Aug. 20 ballot, determining widespread fraud. That pushed Karzai's totals below the 50 percent threshold needed for a first round victory in the 36-candidate field.

The Taliban warned Afghans to stay away from the polls or risk attacks. Dozens of people were killed in Taliban attacks during the August balloting, helping drive down turnout.

President Barack Obama has been waiting for the ballot before deciding whether to send tens of thousands more troops to confront the growing Taliban insurgency. The fraud-marred election cast doubt on whether the Afghan government would be a reliable partner in the fight against the extremists.

The Kabul attack occurred one day after roadside bombs killed eight U.S. service members, driving theAmerican death toll to a record level for the third time in four months.

Such bombs, also called improvised explosive devices or IEDs, are responsible for between 70 percent and 80 percent of the casualties among U.S. and coalition forces in Afghanistan and have become a weapon of "strategic influence," said Lt. Gen. Thomas Metz in Washington.

The attacks Tuesday followed one of the deadliest days for the U.S. military operation in Afghanistan — grim milestones likely to fuel the debate in the United States over whether the conflict is worth the sacrifice.

Obama has nearly finished gathering information on whether to send tens of thousands more American forces to quell the deepening insurgency, White House press secretary Robert Gibbs said. A meeting Friday with theJoint Chiefs of Staff will be among the last events in the decision-making process, Gibbs said.

Both attacks Tuesday took place in the southern province of Kandahar, said Capt. Adam Weece, a spokesman for American forces in the south. The region bordering the Pakistan frontier has long been an insurgent stronghold and was the birthplace of the Taliban in the 1990s.

The Americans were patrolling in armored vehicles when a bomb ripped through one of them, killing seven service members and an Afghan civilian, U.S. forces spokesman Lt. Col. Todd Vician said.

The eighth American died in a separate bombing elsewhere in the south, also while patrolling in a military vehicle, Vician said.

The number of effective IED attacks in Afghanistan has grown from 19 in September 2007 to 106 last month.

Nine coalition forces were killed and 37 were wounded by IEDs in Afghanistan in September 2007. In September 2009, 37 coalition forces were killed and 285 were wounded by IEDs, according to the figures.

The casualties bring to 55 the total number of Americans killed in October in Afghanistan. The next highest toll was in August, when 51 U.S. soldiers died and the troubled nation held the first round of its presidential election amid a wave of violence.

By comparison, the deadliest month of the Iraq conflict for U.S. forces was November 2004, when 137 Americans died during a major assault to clear insurgents from the city of Fallujah.

The deaths came one day after 11 American soldiers were killed in separate helicopter crashes, marking the biggest loss of American life on a single day in four years.

One chopper went down in western Afghanistan as it left the scene of a gunbattle with insurgents. Seven soldiers were killed along with three Drug Enforcement Administration agents — the agency's first deaths since it began operations here in 2005. Afghanistan is the world's largest producer of opium and the trade is a major source of funding for insurgent groups.

Two other U.S. choppers collided while in flight in the south Monday, killing four Americans.

Also Tuesday, NATO-led forces announced they had recovered the remains of three American military contractors from the wreckage of a U.S. Army reconnaissance plane that crashed two weeks ago in Nuristan.

The trio was employed under a Lockheed Martin contract for "counter-narcoterrorism" operations, said Thomas Casey, a spokesman for Lockheed Martin Corp. He said the pilot and co-pilot worked for a company called Avenge Inc., while the technician was employed by a contractor called Sierra Nevada Corp.

The Army C-12 Huron twin-engine turboprop went down Oct. 13 while on a routine mission. The military likely delayed announcing the crash site's location because it did not want to tip off insurgents. Nuristan is believed to be crawling with anti-American militants.

U.S. forces spokesman Col. Wayne Shanks said the crew were the only ones aboard when the craft went down without giving off any distress signal. "We just lost contact," Shanks told The Associated Press.

NATO it was investigating the crash and did not believe hostile fire was involved.

The military also said a UH-60 helicopter traveling to the crash site four days later "experienced a strong downdraft and performed a hard landing" nearby. The helicopter's crew members were rescued, and the chopper was stripped of sensitive and useable parts and destroyed to keep insurgents from salvaging anything in the wreckage.