Updated

The U.N. Middle East envoy says he's alarmed by attacks blamed on Israeli settlers against Palestinian farmers and their olive trees.

Robert Serry says Israel must do more to protect Palestinians and their property in the West Bank, in a statement sent to reporters Sunday. Israel's military had no immediate comment. The West Bank, claimed by the Palestinians for a state, is under Israeli military rule.

An Israeli rights organization, B'Tselem, counts 450 Palestinian-owned trees either damaged or uprooted since the harvest season began on October 10.

Every year a small number of extremist Jewish settlers carry out attacks during harvest season. Most attacks occur close to Jewish settlements in the West Bank. Olive groves provide crucial income for Palestinian farmers.