KABUL - A suicide bomb attack killed seven people and wounded 21 Wednesday outside a U.S. military base in the same part of eastern Afghanistan where militants stormed government buildings a day earlier, police said.

The militant attacks in Khost, a city within sight of the tumultuous border with Pakistan, comes as the U.S. makes leadership changes in Afghanistan that demonstrate a clear break from Bush-era appointees.

A vehicle drove up to the first gate outside Camp Salerno, on the edge of Khost city early Wednesday morning and exploded, said Wazir Pacha, a police spokesman for Khost province. Seven people were killed and 21 others were wounded, the Interior Ministry said in a statement.

U.S. forces confirmed the attack, saying four Afghan security guards were killed in the blast and 12 wounded.

There were no casualties among international troops, said Lt. Cmdr. Christine Sidenstricker, a U.S. military spokeswoman.

On Tuesday, 11 Taliban suicide bombers struck government buildings in Khost city, sparking running gunbattles with U.S. and Afghan forces that killed 20 people and wounded three Americans.

A Taliban spokesman, Zabiullah Mujahid, claimed 30 suicide bombers had attacked the government buildings.

Teams of Taliban militants have launched multipronged assaults on government centres in Kabul, Kandahar and Helmand's capital in the last year, demonstrating an increasing sophistication in their attacks. Military analysts say such attacks are a result of training by Pakistani militants and al-Qaida fighters.

In another example of multidirectional attacks, militants fired several rockets at two other U.S. military bases in eastern Paktika province early Tuesday, the U.S. military said in a statement.

Six militants were killed when U.S. troops used artillery and airstrikes to fire back, the statement said. It said two people not involved in the fight were also killed and four others were wounded.

"We are investigating these actions to determine what happened in Paktika," said Col. Greg Julian, spokesman for the U.S. forces. "We take the safety of Afghan civilians very seriously and sincerely regret this loss of life."

U.S. President Barack Obama has taken charge of the increasingly bloody eight-year war this week, replacing the general in charge of the effort and installing a new ambassador.

The Obama administration hopes the leadership shakeup will help reverse the militants' momentum. Taliban and other insurgent fighters have increased their attacks the last during three years and now control wide swaths of territory.

Obama is also adding troops - more than 21,000 additional U.S. forces are already starting to arrive - to confront the Taliban more forcefully. A record 38,000 U.S. troops are already in the country.

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