One of the rockets landed in Ashkelon's southern industrial zone, near a strategic facility. The rest of the rockets landed south of Ashkelon and in open areas in the western Negev. There were no reports of injuries.
The rockets were fired by members of the al-Quds Brigades, the Islamic Jihad's military wing.
A senior group official told Ynet that his organization would continue to fire rockets as long as Israel continued its attacks, invasions of West Bank cities and villages, and assassinations of group members, many of whom were killed in recent weeks.
The source added that as long as Israel failed to halt these activities, the Islamic Jihad would reject any possibility of a truce.
"It's true that there was no Israeli assassination or an unusual Israeli operation today, but we do not respond when it suits Israel, but when the time and place are right for us.
"Today's firing has no political meaning, in spite of what the Israelis are trying to present. It is part of our responses to the recent assassinations, which killed many of the organization's commanders in the West Bank," he said.
A man working in Asheklon's industrial zone told Ynet, "We heard a very loud whistle and a strong explosion. We were sure that the rocket hit the building. After leaving the fortified rooms we saw that the rocket landed near the facility without causing any damage."
The blasts caused by the Qassams were heard across Ashkelon and in Sderot.
Moyal: Situation becoming more dangerous
Sderot Mayor Eli Moyal heard the blast sounds and understood that the rocket routine was back, despite the Palestinian promises for a truce.
"My opinion regarding the new Palestinian government is no different than that of the rest of Israel's citizens, and therefore we must not have any contact with it.
"We, the area's residents, believe that the situation has become more dangerous now, as this is a total Hamas government, and we must listen to the Gaza Division commander who made very clear statements about the escalation in the area.
"We don’t believe that there will be peace. The Haniyeh government is definitely not brining peace closer and is not preventing the next war. Unfortunately, in spite of my cynicism, such a day is also considered relatively quiet here," he said.
Addressing the ongoing rocket fire, Prime Minister Ehud Olmert said during Sunday's cabinet meeting that there were additional reasons to be disappointed with Palestinian President Mahmoud Abbas, but that ties with him would nonetheless continue.
Shin Bet Chief Yuval Diskin also addressed the strengthening of terror organizations, saying that "Hamas' is becoming stronger mainly in the Gaza Strip. In the West Bank, Islamic Jihad terrorists in Jenin and al-Aqsa Martyrs' Brigades terrorists in Nablus are attempting to carry out suicide bombings."
Ali Waked and Ronny Sofer contributed to the report