Karachi slum: a Pakistani flash point. SIMMERING TENSIONS

The urban landscape of Karachi, Pakistan's largest city, is overshadowed by hundreds of fast-growing slums. Orangi Town, on the city outskirts, is one of those slums. Open sewers line the streets; many of the 1 million residents live in tiny huts, built illegally and lacking sanitation; and a web of organized crime, narcotics, and gun-running has spread noticeably in the past decade. A steady flood of immigrants into the Karachi area has turned Orangi into a flash point for communal violence by aggravating ethnic and political tensions.

In the next decade, half of Karachi's 8 million people will live in slums like Orangi Town, political observers predict. And the question that worries them is: How to stop Karachi's slide into further decay and violence?

``The polarization has begun, the administration has broken down, drug use is widespread, and people are getting guns,'' says Akhter Hameed Khan, a community organizer. ``Young people resent living like this.''

It is partly for this reason, as well as the fact that Karachi is an opposition headquarters, that the government and powerful Army are keeping close watch on the city's volatile situation, political observers say.

``A spark lit in any corner of Karachi suddenly engulfs the entire city,'' says Khanum Gauhar Aijaz, who runs the Public Institute of Policy Studies, a think tank. ``Anything which happens in Karachi cannot remain localized. It immediately spreads all over the country.''

Karachi has long been the destination of millions seeking economic gain and refuge from war. Britain's 1947 partition of the Asian subcontinent brought hundreds of thousands of fleeing Mohajirs (Urdu-speaking immigrants from India) to the city. The 1971 war that split Pakistan and created Bangladesh triggered a new influx of refugees. Wars in Iran and Afghanistan have brought a new flood.

In the last two years, tensions have been reignited by the emergence of Mohajirs as a political force. Claiming discrimination in jobs and college admissions, the Mohajirs are demanding recognition as a new nationality.

Political animosities and Karachi's stagnating economy also have driven the Mohajirs into confrontations with ethnic Pathans, who have moved aggressively to dominate some sectors of the economy and are blamed for the epidemic of drugs and gun-smuggling in the city.

Despite American pressure to control drug trafficking from Afghanistan, officials admit that heroin smuggling continues at worrying levels. Many of Pakistan's more than 2 million drug addicts are in Karachi.

Residents are now taking matters into their own hands. In Orangi, Mr. Khan organized the Orangi Pilot Project in 1980. It has given residents technical advice on how to build and finance sanitation systems. Project officials say about 35,000 houses have received proper sanitation. The project is now expanding to provide family-planning counseling, job-training skills, and improved building materials.