JERUSALEM — A tenuous cease-fire between Israel and Palestinian militants in Gaza Strip was punctured Wednesday by a deadly Israeli airstrike that triggered mortar fire at Israel. After 48 hours in which air attacks were suspended, an Israeli drone strike killed Ismail Asmar, a senior member of the armed wing of the Islamic Jihad group, in his car in Rafah near the border with Egypt, according to the military and local medical officials. An Israeli army statement said Asmar was involved in arms smuggling and efforts by Gaza militants to attack Israel from Egypt’s Sinai peninsula.