Homicide bombers attacked a bus filled with government workers and a commercial area near the Pakistani capital Tuesday, killing at least 25 people and deepening the sense of crisis in a country beset with political uncertainty and Islamic militants.

There was no immediate claim of responsibility for the explosions. Officials suggested the bombings were the work of militants, possibly in response to Pakistani military operations near the Afghan border.

The first explosion devastated the bus early Tuesday as it traveled through a high-security area of Rawalpindi, a garrison city just south of Islamabad and the headquarters of the army.

Interior Ministry spokesman Javed Iqbal Cheema said the vehicle belonged to the Defense Ministry and was carrying employees of various government departments.

He denied reports that the bus was carrying intelligence agency staff, but provided no further details on the victims.

Arif Sultan, who survived the bus attack, told AP Television News that the bomb exploded when the vehicle was waiting in traffic, filling it with flames.

"The roof of the bus was blown away. Pieces of other people's flesh hit my head and covered my clothes," he said from a city hospital bed, where he was being treated for a minor head injury.

He declined to say who he worked for.

As ambulances transported victims from the bus blast, a second bomb carried on a motorcycle went off in a nearby commercial district, killing several more people, said Zainul Haq, a city police official. Two military caps were visible inside one of several cars badly damaged in the second explosion.

Cheema said a total of 25 people had died and 68 more were wounded and that initial investigations indicated that the bombings were suicide attacks.

Religious Affairs Minister Ejaz-ul Haq said the attacks could be a reaction to the war in Afghanistan and Pakistani operations against militants in their strongholds near the Afghan frontier.

A rocket attack on a checkpoint in the South Waziristan border region killed one soldier and wounded four on Tuesday, a local intelligence official said on condition of anonymity because he is not authorized to speak publicly.

Local militants say they abducted scores of Pakistani troops in the same region last week.

"This is all probably because of the situation presently in Afghanistan and in Waziristan," Haq said on Dawn News television. "We are the front line state in the war against terror, and we are suffering the most."

Pakistan has witnessed scores of bombings and other acts of terrorism since siding with the United States after the Sept. 11, 2001, attacks. Officials have blamed pro-Taliban and al-Qaida elements for much of the violence.

Cheema said authorities were examining whether Tuesday's attacks were linked to two suicide attacks in Islamabad in July that killed 31 people.

Rawalpindi has also seen several attacks, including two huge bombs aimed at President Gen. Pervez Musharraf that killed at least 16 people, including three suicide attackers, in December 2003.

Musharraf, who seized power in a 1999 coup, is under pressure from Washington to crack down on extremists in the border region amid U.S. claims that Al Qaeda may be regrouping there.

The general is currently trying to negotiate a pact with exiled former Prime Minister Benazir Bhutto to shore up his troubled re-election bid and form an alliance of moderates.