Around 400 Egyptian activists headed to the Gaza Strip on Sunday to show solidarity with its people as Israeli air strikes pounded the Palestinian enclave for a fifth day, organisers said. A five-bus convoy transporting members of several Egyptian parties and political movements arrived at the country\'s Rafah border crossing with Gaza, officials said. \"The trip is aimed at showing our support for the people of the Gaza Strip in the face of the Israeli aggression,\" said organiser Mahmud Ali of Egypt\'s liberal Dustoor Party. The activists were \"carrying a message of support from the people of Egypt,\" he added. They were also bringing medicine and emergency medical supplies. \"We all entered through Rafah border... 100s now attempting to enter Gaza,\" activist Gigi Ibrahim said on her Twitter account. Israeli air strikes on Sunday killed at least 21 Palestinians in the bloodiest day of its massive air campaign to halt rocket fire from the Gaza Strip. Since the operation was launched on Wednesday, 67 Palestinians have been killed and more than 600 injured, while three Israelis have died and more than 50 have been injured by rocket fire. Egypt is at the centre of efforts to broker a ceasefire. Security officials in Cairo said an Israeli envoy also arrived in the Egyptian capital on Sunday for talks.