P115ORACLE 115 Fri18 Apr ITV 1637:44        El Salvador: Two senior army officers have been arrested and a third is being hunted is connection with a series of kidnaps for large ransoms.  Chile: Riot police backed by troops raided three universities in Santiago and arrested 500 students after protests against the Pinochet govt.  Costa Rica: Four people, including a Nicaraguan, were arrested after a bomb blast at the US consulate in San Jose.       see 125