The first weekly prayers since the start of air strikes on Afghanistan became a call to arms against America at Egypt’s foremost Islamic institute today.

But hundreds of riot police around Al-Azhar made sure the anti-American protest did not reach the Cairo streets, and the cleric who led prayers, Grand Sheik Mohammed Sayed Tantawi, was careful not to criticise Washington.

‘‘It is the right of the country that has been attacked to retaliate, but it shouldn’t kill innocent people,’’ Tantawi said.

As soon as Tantawi finished his sermon, worshippers took the microphone.

‘‘God make Afghanistan a grave for the Americans, as it was for the atheists,’’ shouted an man, referring to the Soviet Union’s 1979-1989 occupation of Afghanistan.

A leading member of the Muslim Brotherhood, Ahmed Seif Al-Islam Hasan al-Banna, told the 5,000 worshippers the air strikes were a disgrace.

‘‘America says it is in a war against terrorism, what is terrorism? ... Eventually we are all going to be labelled terrorists.’’