Peshawar, Pakistan ? A suicide bomber detonated his charge inside a crowded restaurant during the lunch hour Tuesday, killing 25 people and adding to a string of violent episodes that have badly shaken the government of President Pervez Musharraf.

In just four days, Pakistan has been the scene of urban rioting that killed 40, a border clash with Afghanistan, the death of a U.S. soldier and the suspected assassination of a top official at the Supreme Court.

Although not all of the incidents have been related, they have underscored the diverse challenges to Musharraf’s authority. As Islamic militants have carried out attacks aimed at undermining his rule, pro-democracy advocates have taken to the streets to condemn what they see as authoritarian tactics. Calls for the president’s resignation have grown louder, and there is open talk that the country could descend into broader civil disorder.

“Musharraf is losing control,” retired Lt. Gen. Talat Masood, an independent security analyst, said in an interview. “This is a failing state, if not a failed state.”

The blast in Peshawar was blamed on pro-Taliban insurgents who operate along the border between Pakistan and Afghanistan, and it was apparently aimed at sending a message not to cooperate with the United States on counterterrorism. Musharraf, a general who seized power in a bloodless coup eight years ago, has been considered a vital U.S. ally against al-Qaida and related terrorist groups since 2001.

The suicide bombing hurled glass and body parts into the street and obliterated the inside of the restaurant, which was on the first floor of a modest hostel.

Hundreds of irate and anxious relatives converged at a nearby hospital to await word of their loved ones’ fate. A message board listing the injured featured more than 20 names.

“My cousin was eating his food when he felt the blast and he fainted,” said Salman Shah, 23, who was among those gathered near the board. “When he came back to life, his hand was gone.”

The restaurant, which served Afghan food, was popular among both Afghans and Pakistanis in this teeming city, which sits at the edge of the uneasy border region. Most of those killed were Afghan, officials said, and the dead included a woman and a 7-year-old child.

Investigators recovered the bombers’ legs, which had notes attached to them with tape. “The message was that anyone helping the U.S. would meet a fate like this,” said Abdul Majeed Khan, a police chief in Peshawar.

Other senior police officials, who spoke on condition of anonymity, said the owner of the hostel had tipped off the Pakistani intelligence service about suspected Afghan militants who were staying at the hostel. At least one arrest based on the tip was made Saturday.