A senior source in the Palestinian Authority told Haaretz Sunday that he suspects Hezbollah or another organization with links to Iran was behind the attempted bombing of the Lev Hamifratz shopping mall in Haifa on Saturday night.

According to the source, the PA holds definitive intelligence that Hezbollah has been trying for some time to recruit members of Fatah, Hamas and Islamic Jihad in an attempt to get operatives of those terror groups to carry out an attack in Israel.

The aim of the Lebanese Shi'ite group is to carry out a massive terrorist attack that would avenge the assassination of its mastermind terrorist, Imad Mughniyeh, in Damascus in February 2008, the Palestinian source said. Hezbollah blames Israel for Mughniyeh's death.

Last week, two police officers were killed in the Jordan Valley, and an anonymous caller claimed responsibility in the name of the Mughniyeh Units.

In recent weeks there has been a slight increase in the number of attempted attacks on both sides of the Green Line, leading security forces to examine the possibility that some of the events may be linked. All the same, a Shin Bet security service official said there was nothing to suggest an overall upsurge of terror.

"During the past months there have been warnings for pending attacks," the source said yesterday. "But we do not identify an unusual trend suggesting a renewed wave of terrorism."

The investigation of the attempted bombing, some details of which are still under a gag order, suggests that it was an unusually sophisticated plan, and officials suspect the know-how came from abroad.

The terror attack was thwarted when police sappers disarmed a bomb weighing dozens of kilograms in a car outside the mall Saturday night. An organization calling itself the Galilee Freedom Fighters claimed responsibility Saturday, but security officials said they doubted the veracity of the claim.

The bomb had the potential to cause enormous destruction, said Yossi Malka, a police sapper involved in defusing the bomb.

"We can compare the potential blast to 15 suicide bombers exploding at once," he said.

As a result of the bombing attempt, security at malls and public institutions throughout the city was stepped up Sunday.

Police are trying to locate a woman who reported to a mall security guard that a sedan had exploded in the unguarded parking lot near the mall and that its trunk had popped open. The guard, who had seen the car entering the lot at high speed a few minutes earlier, called the police.

Sappers said one part of the device had gone off prematurely and another had failed to detonate.

Eli Gatnio, the first sapper to reach the car bomb, said there were dozens of kilograms of explosives and metal balls in a bag, which "were packed into various packages that included all the components of a bomb." He identified the car as containing a "live bomb," rather than merely a vehicle that aroused suspicion, and got into the car to disable the explosive immediately. He was joined by three other sappers several minutes later.

"The immediate urgency of dismantling the bomb and the presence of so many people in the area meant that we had to feel and smell the explosive, physically deal with the components rather than doing it from a distance, with a robot," said Gatnio. "Most of the bomb was dismantled by hand."

The entire operation lasted about half an hour, though the lab analysis of the evidence and the search for suspects in the area took longer.

"During the incident we are focused and think of nothing else, not children, or family," Malka said, attributing his officers' skill to their training.

Outgoing Prime Minister Ehud Olmert said Sunday that a "miracle" had prevented a huge terror attack from taking place in Haifa. The prime minister also said Hamas was seeking to establish itself in the West Bank and use it as a base for terror attacks against Israel.

"We are treating the attempted attack in Haifa with great gravity," Olmert said at the start of the weekly cabinet meeting. "A huge disaster was prevented by a miracle."

"We shouldn't delude ourselves - attempts at terror attacks have continued and will continue," he said.