By Nidal al-Mughrabi and Allyn Fisher-Ilan GAZA/JERUSALEM (Reuters) - Israel kept up its assaults in the Gaza Strip on Tuesday, killing three Palestinians in as many air strikes, as U.S. Secretary of State John Kerry arrived in the region with a mission to seek a ceasefire in the 14-day-old conflict "as soon as possible." The deaths in Khan Younis, Beit Hanoun and Beit Lahiya raised the Palestinian toll to 539 killed, including nearly 100 children and many other civilians, since the offensive was launched on July 8, Gaza health officials said. Israel's death toll also rose to 29, with two soldiers killed in the past day of fighting, the Israeli military said. Israel said a Palestinian shot at a car and seriously wounded an Israeli in the Nablus area on Tuesday. Kerry arrived in Cairo on Monday and, during talks with United Nations Secretary-General Ban Ki-moon, said the United States would provide $47 million in humanitarian aid for Gaza.