The State Department cautioned Americans anew yesterday about terrorist attacks in Lebanon on the basis of "new information concerning threats across the board to Americans," including members of the press.

Spokesman John Hughes said his spoken warning, at the department's daily news briefing, was intended to supplement the "travelers' advisory" issued by the State Department May 15 urging Americans to avoid travel to Lebanon.

The occasion for the new warning was a report that four Lebanese employes of the Associated Press had disappeared in Beirut en route to work.

Terry Anderson, AP chief Middle East correspondent, said it was believed the four men had been abducted or seized in mostly Moslem west Beirut, but that it was not known by whom.

The State Department spokesman said the volume of reported threats against U.S. diplomatic posts and personnel is "very great." Hughes said that the various reports, including some about the movement of people, resources and money around Lebanon and the Middle East, are "a very mixed bag," with many reports proving to be groundless.

He declined to say specifically how many threats or reports of threats have been received since the numbers began to increase substantially around the time of the terrorist bombing of the U.S. Marine headquarters in Beirut a year ago. Another official said 100 threats per week against U.S. installations worldwide is "about as good a number as any" to describe a situation in which there are great fluctuations in extent, intensity and location.

Hughes said he was speaking out now because Beirut and Lebanon is "a high-risk area" where the United States recently suffered the bombing of its embassy annex last month. "We're trying to be prudent as far as U.S. government officials in the area are concerned" and want to pass along the caution to journalists and other private Americans still in Lebanon, Hughes said.

Officials have expressed special concern about possible attacks on Americans before the Nov. 6 election, believing that some terrorist groups would like to strike in this period in the hope of affecting the U.S. balloting. This concern is not limited to the Middle East but extends to Central America and other areas, officials said.

The State Department has been drastically reducing the number of Americans on duty at the embassy in Beirut. The department said that the number of employes, including temporary duty personnel and military training teams, declined to 99 by the time of last month's bombing and to 45 by last Friday. The number is believed to be even smaller now, though the department refused to release it.