After meeting John Negrouponte, the US deputy secretary of state, Musharraf reaffirmed "Pakistan's firm resolve to fight extremism and terrorism".

The country is under growing pressure from Washington to crack down on Taliban and al-Qaeda fighters in the regions along the border with Afghanistan.

'Paramount concern'

"The terrorist threat in the border areas is of paramount concern to many countries," a Western diplomat in Islamabad told Reuters news agency.

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"They want Musharraf to resolve the political situation and move back into focus on this danger as soon as possible. There is huge concern that Pakistan is being distracted by its internal situation," the diplomat said.

Helicopter gunships and artillery killed scores of fighters in the Waziristan border region, according to an army spokesman, during the two days Negroponte was in Islamabad.

Nine months ago, when he was US intelligence chief, Negroponte spoke of the global threat posed by al-Qaeda fighters regrouping in Pakistan, the need to eliminate safe havens for the Taliban in Pakistani tribal areas, and described the country as "a major source of Islamic extremism".

Negroponte led a delegation aimed at developing long-term business, energy, education and defence ties with Pakistan, but he was also accompanied by Dell Dailey, US ambassador at large and counter-terrorism co-ordinator.

Karachi attack

Meanwhile, armed men on motorcycles killed at least six people when they attacked a bus in the southern city of Karachi with a hand grenade and gunfire.

 Four of the dead on the bus were from the 
student wing of Jamaat-i-Islami [AFP]
Four of the dead were from the Islami Jamiat Tulaba (IJT), the student wing of the Jamaat-i-Islami party.

Mohammed Danish, a spokesman for the IJT, blamed the rival Mutahida Qami Movement (MQM) for the attack, although he did not offer any evidence to back up his claim.

MQM mainly represents Urdu-speaking migrants in Karachi. Jamaat-i-Islami is Pakistan's largest Islamic party.

Azhar Faruqi, the city's police chief, called the attack an "act of terrorism" but provided no further details.