Palestinian fighters wounded 12 soldiers in a rocket attack on Israel on Wednesday, defying calls for a ceasefire from Mahmoud Abbas, the frontrunner to succeed Yasser Arafat in an election on Sunday. Israeli soldiers have killed more than 20 Palestinians in Gaza in the past week, including seven youths aged from 11 to 17 who died on Tuesday from a tank shell which the army said was aimed at a militant rocket crew. The escalating violence comes despite calls by Abbas for an end to the salvoes from Gaza to allow talks on a state in occupied lands to resume with Israel after four years of a Palestinian uprising. Israeli Prime Minister Ariel Sharon, raising doubts over new hopes for peace following Arafat's death, said he did not think the Palestinians could achieve anything if violence continued. The rocket crashed inside the Nahal Oz army base just beyond Gaza's border fence. Hamas militants said they were avenging the killing of the seven Palestinians in a Gaza strawberry farm. --More 2317 Local Time 2017 GMT