During the 1950s, Syria mounted a propaganda campaign against Abdallah and granted political asylum to opposition elements from Jordan, including political asylum in 1957 to Jordanian Army officers and civilian politicians who had conspired to topple King Hussein. Tensions mounted in 1958 when Hussein's private jet en route to Europe was intercepted by Syrian MiGs and forced to return to Amman. Also, Syrian-trained groups infiltrated Jordan to carry out subversive acts, culminating in the August 1960 assassination of Jordanian Prime Minister Haza al Majali, whose killers escaped to Syria.