Acting President Ghulam Ishaq Khan appealed for calm on Wednesday amid fears of more sectarian violence provoked by the suspected assassination of his predecessor, Mohammad Zia-ul-Haq.

Troops were called out in Karachi, the country's biggest city, as a precaution during mourning processions by Shi'ite Moslems marking Ashura, the holiest day of the sect's religious calendar.Ishaq Khan, who took office after Zia was killed in a mystery plane crash a week ago, said in a statement Pakistan was facing "external and internal threats."

He said he was deeply distressed to see Pakistanis "split on linguistic, parochial, regional and tribal lines" and urged them to forge unity and sectarian harmony.

Opposition politicians have also appealed for calm.

More than 5,000 troops were deployed at Shi'ite holy places in Karachi to guard against trouble on Ashura, often marked by bloodshed between Shi'ite and Sunni Moslem sects.

Tension between the two sects soared after some Shi'ites rejoiced at Zia's death, provoking clashes with Sunnis in a northwestern tribal belt where at least nine people died.

Zia, a Sunni, was unpopular among Pakistani Shi'ites, who form about 15 percent of the Sunni-dominated population of 103 million but are the majority in neighboring Iran.

Pakistan's generally pro-Iranian Shi'ite leaders mistrusted Zia's pro-Western policy.