Chinese President Hu Jintao has expressed concern about the "humanitarian crisis" in Gaza while talking to US President George W. Bush, Israel's most powerful ally, the foreign ministry said here. "We are very worried about the humanitarian crisis that has emerged in the Gaza Strip," Hu told Bush in the telephone conversation, which happened late Sunday, according to a statement on the ministry's website. Hu "expressed concern about the escalation in the conflict between the Palestinians and the Israelis and the worsening turbulence in the Middle East," the statement said. "We hope that the relevant parties will immediately stop their military activities and armed clashes and relax the situation in order to create the conditions for a solution to the conflict by political means," Hu said. Israeli ground forces moved into Gaza over the weekend after days of air and naval raids. The death toll had passed 510 as of early Monday. The military offensive, Israel's largest since its 2006 war with Lebanon, is aimed at ending rocket and mortar attacks by Hamas and its militant allies. China, a permanent member of the United Nations Security Council, has repeatedly expressed its concern over the situation in Gaza since Israel began its campaign against Hamas on December 27. Aid groups have said Israel's offensive had aggravated a humanitarian crisis for Gaza's population, who have no electricity, no water and now face dire food shortages. Hospitals were only running on backup generators.