Taliban suicide attackers who detonated a truck bomb early Tuesday at the gates of a NATO supplier's compound in Kabul and sprayed gunfire at security personnel killed at least 7 people, including an American, a western contractor familiar with the facility said.

The source has told Fox News that an American civilian and Romanian are among the dead, and 30 others are injured, seven in critical condition. Afghan officials say five guards and two civilians were killed in the attack, which lasted two and a half hours, according to the source.

The assault was the latest in a series targeting high-profile locations in the Afghan capital. The attacks have made clear the Taliban have no intention of ending the violence, even as they say they are willing to enter peace negotiations.

The U.N. deputy chief, Jan Eliasson, who was in Kabul wrapping up a five-day trip to Afghanistan when the attack took place, said continued violence could only harm the Taliban's own cause.

"I would hope that there would be steps taken by the leadership of the Taliban to realize that the tool of violence in any case cannot instill confidence in the population," he said. "There's been too much suffering there and there are too many widows, too many father-and-motherless children in Afghanistan and I think we need to instill a sense of calm."

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    But the Taliban showed no signs of backing off, telling The Associated Press by phone that Tuesday's attack was part of its offensive started in the spring to target military and diplomatic sites with suicide bombers.

    "This has no link to the peace process," the militants' spokesman Zabiullah Mujahid said. "It will continue all over the country occupied by the foreigners."

    The attack started before dawn, when a suicide bomber drove a small truck to the outer gate of the logistics center used to supply NATO troops and detonated it. The explosion made a massive crater in the ground and damaged a guard tower, said Kabul provincial police chief Mohammad Ayuob Salangi.

    Two truck drivers waiting nearby to enter the compound were also killed in the blast, along with the bomber.

    Four gunmen then stormed into the breach and battled with security guards, and an Afghan police special response team that was called in, for about an hour before being killed, the Interior Ministry said in a statement. One Afghan and four Nepalese guards were also killed, the ministry said.

    Mujahid quickly claimed responsibility for the assault, saying it was "a very effective attack that embarrassed the enemy."

    In a statement on the Taliban website, Mujahid said only three militants were involved in the "attack on a big foreign base important for NATO logistics," and listed them by name.

    The Taliban last month opened a new political office in the Gulf nation of Qatar, and indicated that they were prepared to enter into Afghan peace talks, but at the same time did not renounce violence.

    The following week, Taliban suicide attackers were able to get past preliminary security checks and open fire on guards at a gate to the presidential palace in a bold attack at the heart of the Afghan government.

    Earlier in June, heavily armed fighters launched a failed assault on NATO's operational headquarters at Kabul's international airport and blew up a car bomb outside Afghanistan's Supreme Court.

    Eliasson said if U.N. support was needed to help start the peace process, he was glad to provide it -- but only if requested by the Afghan government.

    "The reconciliation process must be, if it is to be successful, Afghan-led," he said. "What I hope will take place is, of course, contacts between the two parties ... and as long as those contacts continue, there's no specific need for the United Nations to be involved."

    Also Tuesday, in the eastern province of Paktika, local police commander Azizullah Karwan said six Taliban militants were killed in a clash with one of his patrols.

    He said no police were killed or injured.

    Fox News' Dominic Di-Natale and the Associated Press contributed to this report.