KABUL, Afghanistan -- Rebel rockets struck US troops unloading supplies from a helicopter in eastern Afghanistan yesterday, killing two and wounding eight in one of the bloodiest assaults on American forces since insurgent violence picked up in March.
The killings came a day after the Afghan government warned that Taliban and Al Qaeda fighters are waging a campaign of violence in hopes of undermining legislative elections in September, although the rebels failed to disrupt last fall's presidential vote.
After the explosions at the base in Shkin, 4 miles from the border with Pakistan, US warplanes and attack helicopters rushed to the scene to search for the attackers, but found no trace of them, Lieutenant Colonel Jerry O'Hara said.
The US spokesman said four rockets hit the base.
''This was a serious attack against coalition forces," O'Hara said. ''Security is not as good as it should be. But when you look at it over the course of months, incidents are on the decline. But that doesn't appear to be the case today."
O'Hara said the Shkin base is part of an operation along the border to prevent ''foreign fighters from entering into this country to derail the peace process."
Militants based in tribal regions on the Pakistani side of the mountainous frontier often cross into Afghanistan to launch attacks, Afghan officials say. Seventeen suspected Taliban rebels were reported captured in the border area Monday.
The wounded were flown to other bases for treatment, O'Hara said.
Their names and military branch were being withheld until families could be notified.
The two deaths brought to 148 the number of US military personnel killed in and around Afghanistan since Operation Enduring Freedom drove the Taliban from power in late 2001, according to Pentagon figures.
Late last week, two US soldiers were killed and another wounded when a bomb exploded near a military convoy, also in eastern Afghanistan near the border.
Even though US officials express optimism about progress toward making Afghanistan secure, there has been a sharp rise in bombings, shootings, and other violence since winter's snow melted in mountain passes used by the rebels.
Security forces have hit back hard, killing more than 200 suspected rebels since March, US and Afghan officials say.
A spokesman for President Hamid Karzai, Jawed Ludin, charged Tuesday that Al Qaeda and Taliban rebels launched a violent campaign last week to subvert the Sept. 18 legislative elections -- the next key step toward democracy three years after US-led forces toppled the Taliban for harboring Osama bin Laden and Al Qaeda military camps.
Ludin said the campaign started with a June 1 suicide bombing in the southern city of Kandahar that killed 20 people and a failed attempt on the same day to shoot down a US military aircraft with a shoulder-launched missile. He said the militants seek to create ''maximum shock among the people."
On Tuesday, suspected rebels attacked a Pakistani-owned fuel tanker after it delivered gasoline to a US base in the southern Afghan district of Spin Boldak, killing the Pakistani driver and his assistant. Five suspects in the attack were captured yesterday, police said.
Meanwhile, the Afghan government said yesterday that negotiations to free a kidnapped Italian aid worker, CARE International's Clementina Cantoni, were ''close to a conclusion."