BOSTON (AP) _ Break-ins in at least six cities reportedly have some sanctuary groups worried that they are the targets of a campaign of harassment.

Legal files, mailing lists and records of telephone conversations have been reported stolen from churches and offices in Seattle, Detroit and Guadalupe, Ariz., The Boston Globe reported today.

Activists opposed to U.S. policy in Central America also report files and mail being rifled at offices in Cambridge, Phoenix, Ariz., and Philadelphia, the newspaper said.

In the latest reported break-in, five offices in the Old Cambridge Baptist Church, four of them housing political or sanctuary groups, were ransacked Thursday.

Garrett Brown, director of the New Institute for Central America, told the Globe that drawers in his office had been opened, files scattered and mail opened.

The break-ins and surveillance incidents constitute ''a pattern of harassment and intimidation,'' Adelita Medina of the Movement Support Network, a nationwide sanctuary group, told the Globe.

No arrests have been made in any of the incidents, Medina said.

Some sanctuary workers and political advocates think the break-ins may be the work of right-wing activists, but others say they tend to suspect government agents, the Globe reported.

But FBI spokesman Lane Bonner denied the government is involved, saying, ''The FBI does not engage in that kind of activity.''

If the activists believe there is a conspiracy to violate their civil rights, he said, they should request action from the Justice Department.