Israeli troops erected roadblocks throughout the occupied West Bank and Gaza Strip to prevent Jewish settlers from staging demonstrations against what they say is Israel’s failure to protect them from Palestinian violence. There are about 65,000 Jewish settlers living in the occupied territories. At the same time, hospital officials in Jerusalem said an 18-year-old Arab died of wounds sustained in a clash with troops last week in the West Bank, and an Arab reporter said a 16-year-old Palestinian youth was shot and wounded in a clash in Gaza City. In an Arab village in northern Israel, police arrested a Palestinian accused of killing his landlord’s two sons and wounding their mother when the family refused to sell him an apartment. The accused, a policeman in the occupied territories, had been accused of collaborating with Israeli authorities.