Government forces battled fighters in a northwestern Pakistani province on Wednesday as rumors circulated of a possible state of emergency to arrest the worsening security situation in the country, prompting Benazir Bhutto to cancel an overseas trip to visit her family.

On Wednesday, Pakistani security forces clashed with fighters in a mountain valley in the North West Frontier Province, leaving up to 18 men dead.

A provincial official said the fighting began after a helicopter was attacked about 15km north of Mingora, Swat valley's main town.

Badshah Gul Wazir said the fighters had fired at the helicopter as it flew over Matta area.

The clashes came a day after a suicide bomb attack less than a kilometer from the army headquarters in Rawalpindi killed at least seven people, including policemen and civilians, and left 11 others wounded.

Visit cancelled

Also on Wednesday Bhutto, Pakistan's former prime minister, abruptly cancelled plans to visit her family in Dubai in the UAE.

She said she heard rumors that the government could impose a state of emergency during her absence.

"If a state of emergency is imposed, we will not accept it," she said.

"If fundamental human rights are suspended, we will not accept it. The nation will not accept it, and I know other political parties will also not accept it."

She said senior aides in her Pakistan People's Party told her that Pervez Musharraf, Pakistan's president, might impose emergency measures if his recent election victory was declared unconstitutional by the supreme court, claims the government denied.

A ruling is expected later this week. Musharraf has pledged to quit the army before starting a new presidential term.

Court impatience

Bhutto has been targeted by suicide bombers since she returned home on October 18 following eight years in exile.

In a related development, the country's most senior judge expressed impatience on Wednesday with the investigation into the bomb attack on Bhutto's convoy in Karachi.

Chief Justice Iftikhar Mohammed Chaudhry, who heads the supreme court, said he would open his own investigation.

The supreme court will review the bombing to ensure the "perpetrators of this barbaric act are brought to book, which will result in restoring the confidence of the nation in the system of governance", a court statement said.

The case is scheduled to be heard on Thursday.

PHOTO CAPTION

Pakistani paramilitary troops stand on alert at a check post on the outskirts of Mingora, the main town of Pakistan's Swat valley. [Reuters]

Al-Jazeera