MANILA, Philippines (AP) _ Presidential security guards charged a flag bearer with threatening President Corazon Aquino during opening ceremonies for the Chess Olympiad, police said Monday. But the flag bearer said he was only joking.

Francisco Opao was detained on charges of making grave theats by members of the Presidental Security Group who said they heard him say he would ''skewer'' Mrs. Aquino with the flagpole he carried.

Aquino and world chess champion Garry Kasparov made the symbolic opening moves Sunday to begin the three-week, 92-nation competition.

Opao, 42, said he spoke in jest after another flag bearer made a similar remark.

''I just repeated her joke, but it was me that the PSG heard,'' Opao told reporters. ''I was startled when they grabbed me and took me away from the march. I hope President Aquino forgives me for what I did.''