Avoid places where fellow Americans congregate, even churches and schools. Drive to work a different way each day, with the windows up. Be cautious. Remain vigilant.

The government is giving Americans overseas those warnings after a weekend attack on a church in Islamabad, Pakistan, that killed five people, including an American woman who worked at the U.S. Embassy and her teen-age daughter.

Because embassy buildings and overseas U.S. military bases are now so fortified against attacks, terrorists increasingly might turn to more vulnerable targets — including schools, restaurants and even churches — where Americans gather, the State Department warned Monday.

``One would have hoped that there would be some respect for a church,'' said State Department spokesman Richard Boucher. ``But even that doesn't always exist.''

Total security is impossible, officials acknowledge. Private companies and the government need to have workers overseas, and those workers often want their families nearby. If families are nearby, they must do things like shop and go to school.

In recent months, some U.S. companies with operations in the Middle East or south Asia have chosen to relocate workers' family members to another location, like Europe, still close enough for frequent visits, said Vince Cannistraro, a former government counterterrorism official who runs his own security business.

Others are cutting back on the number of Americans overseas, relying instead on more local workers.

Still other U.S. companies are spending thousands of dollars to add guards and improve the physical security at compounds where their employees live, Cannistraro said.

The U.S. military makes many of its bases in Middle Eastern countries and other hot spots ``unaccompanied,'' meaning that spouses and children cannot go along. But that is viewed as a hardship, and thus rotations have to be frequent, costing more money.

It can be tricky to know when a place is safe.

The Americans killed in Islamabad — Barbara Green, an employee at the Embassy, and her 17-year-old daughter, Kristen Wormsley — chose to leave Pakistan temporarily after Sept. 11, with State Department authorization, because they felt conditions were too dangerous.

In late January, the embassy concluded the situation had improved and allowed them and other departed Americans to return.

``The people at posts were looking forward to having their families back with them,'' Boucher said. ``And at that time, we operated on the best security information we had.''

Another 14 Americans — all private citizens — were injured in the Islamabad church attack.

Terrorists have always looked for ``soft'' targets when their primary goal — military bases and government offices — have proved difficult to reach.

Fifteen years ago, in an attack blamed on Libya, two U.S. soldiers were killed in a bombing at a West Berlin disco. In 1997, four American auditors of a U.S. oil company and their Pakistani driver were killed while traveling in Karachi, Pakistan, between their hotel and work.

Now, military bases and embassies are fortified more than ever before with high walls, concrete barriers, sophisticated cameras, armored vehicles and guards with machine guns.

``If you're going to exact some revenge against Americans, you look for softer targets. (Journalist) Daniel Pearl was a softer target. They went after him,'' Cannistraro said.

Schools are one of the biggest concerns, many government and private security officials say.

After the USS Cole bombing in Yemen in October 2000, some U.S. embassies in the Middle East asked American employees to keep their children home from school for a few days, so security could be scrutinized.

In some cases, children travel to schools in buses without any armed guards, even while their homes are heavily guarded, said a State Department official, who spoke on condition of anonymity.

Embassy security officers often work with the private schools to improve security, trying to ensure, for example, that buses vary their routes each day, the official said.