Seven mortar rockets have been fired into southern Israel by Palestinian militants.
The Viva Palestina convoy, led by MP George Galloway, has been delayed at the Kerem Shalom crossing after three struck near the boarder.
Three more shells hit the north west Negev and another on the coastal strip. No-one was injured or killed.
IDF Major General Yoav Galant of the GOC Southern Command warned Negev citizens that they should prepare for further attacks.
He said: "It's true that we are after the first rains and the sun is shining - but one can see dark clouds in the distance."
The Popular Resistance Committee militant group claimed responsibility for firing the rockets, claiming it was a retaliation for an Israeli Air Force strike two days ago, where a regional commander was killed.
Army helicopters later dropped leaflets in Gaza warning them to stay 300 metres from the security fence for their own safety, and urging them not to become involved with smuggling in the Gaza tunnels.