Two homicide bombers blew themselves up at a naval college on Tuesday, killing four people and underlining the security challenge facing the winners of Pakistan's landmark elections.

Authorities detained eight people, all allegedly members of outlawed Sunni Muslim militant organizations, in separate raids hours after the bombing, said Chaudhry Masood Aziz, chief of anti-terrorism for the police department of in the eastern city of Lahore.

The men were picked up "in an attempt to find any clue to identify the bombers or people involved in the attack," he said. None was a suspect, he said.

The bombers rode up to the gate of the college's parking lot on a motorcycle. The passenger dismounted and destroyed the gate with a bomb, allowing his accomplice to ride inside and unleash a much more powerful blast, said police Chief Malik Iqbal.

Muhammad Safdar, a 23-year-old chauffeur, said he had dropped off an officer at the college and was sitting in the cafeteria when he heard the first blast and rushed outside.

"There was smoke and vehicles on fire ... Several people were lying on the ground injured and crying for help, but I, too, was injured as something hit me in the neck," he told reporters.

Pakistan Navy War College, which trains senior naval officials from Pakistan and other countries, is the latest target in a bombing campaign that has killed hundreds in recent months and relented only briefly during the Feb. 18 parliamentary elections.

In Washington, State Department spokesman Tom Casey told reporters the United States condemned the attack and offered its sympathies to the victims and their families.

Terrorists in Pakistan "are willing to use any and all" techniques to carry out their objectives, he said. Continuing attacks show the importance of the U.S. working with the government to fight extremism, he said. "We want to be able to work well with the new Pakistani government once it's formed," Casey said.

Asif Ali Zardari, co-chairman of the party expected to lead the new government, called the bombing as "inhuman, barbaric and most despicable."

Pakistanis must unite against "conspirators and extremists," said Zardari, the widower of opposition leader Benazir Bhutto, who was assassinated in a gun and homicide bomb attack in December.

President Pervez Musharraf said the government "would not be cowed down by such acts," vowing to "continue the fight against extremism and terrorism," the state-run Associated Press of Pakistan news agency reported.

The four dead and 14 wounded were all employees of the college, Iqbal told reporters. None were senior military officials, he said.

The police chief said it was too early to speculate about who was responsible for the attack.

On Friday, homicide blasts killed 40 people at a funeral for a slain police official in the restive Swat Valley. About 40 tribal elders died in another homicide attack Sunday as they discussed setting up a militia force to combat militants near the Afghan border.

The violence increases the pressure on moderate, pro-Western parties who triumphed in the vote to form a government and review government strategy against the militants.

However, the parties of Bhutto and Nawaz Sharif, another former prime minister, have said their priority is reducing the sweeping powers accumulated by Musharraf since he seized power in a 1999 coup.

Mullen, the top U.S. military official, was making his second visit to Pakistan in a month, emphasizing concern in Washington at the growing strength of Al Qaeda and Taliban militants.

Mullen and Musharraf, who has been a key ally in the U.S.-led war on terror, discussed the "regional security situation and the measures being taken to address it," the news agency said.

Mullen also conferred with Gen. Ashfaq Parvez Kayani, who replaced Musharraf as army chief in November as part of the country's transition back to democracy after eight years of military rule.

Details of the talks were not released, but Mullen was expected to discuss U.S. military assistance including plans to send American counterinsurgency experts to Pakistan this year to help train a paramilitary force on the front line of the battle with militants near the Afghan border.