SARGODHA, Pakistan, Nov 1 (Reuters) - A suicide bomber rammed an Air Force bus in Pakistan on Thursday killing 8 people while troops killed up to 70 militants in the northwest, as rumours swirled President Pervez Musharraf could invoke emergency rule.

Nearly 800 people have been killed in militant-linked violence and there have been more than 22 suicide attacks in the last four months, heightening concerns about the stability of nuclear-armed Pakistan at a time when U.S. ally General Musharraf is trying to engineer a transition to civilian-led democracy.

The second suicide attack this week targeted a bus taking personnel to an air base in Sargodha in the central province of Punjab, the military said.

"Eight people have been killed including four officers," military spokesman Major-General Waheed Arshad said, adding civilians were among those killed. An air force statement said 27 people were wounded.

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