Nine people were arrested by Zichron Ya'acov police on Sunday for throwing rocks at vehicles near the entrance to Jisr e-Zarka over the weekend, one of an increasing number of such incidents across the North. The three adult suspects had their custody extended by six days, while the other six suspects arrested were minors, police said. Despite the mushrooming of instances of Arab Israeli youths hurling stones at cars - a 62 percent rise was recorded between 2006 and 2007 - with another marked increase over the weekend, police officials shied away from attributing a nationalistic motive to the rock throwers. "Most of the people arrested are minors, although some are older. We can't give a clear motive," Zichron Ya'acov police spokesman Moshe Weizman told The Jerusalem Post. "Some of this is juvenile delinquency. Sometimes these youths are sent by others. Some cases could be tied to the security situation in Gaza. But we're being careful about motives here," he said. Weizman said Zichron police had employed a range of methods to tackle the problem, including "undercover operations, and dialogue with community leaders. We're trying to do it all, and as you can see we've made some arrests." "I do not see this phenomenon escalating at this point," he added. "The punishment stipulated by law for rock-throwing is 20 years in prison, though the maximum sentence has never been handed down," Weizman said. "It's tantamount to attempted murder, and throwing a rock at a moving car is extremely dangerous," he said. "But it's difficult to know if it's vandalism or nationalistically motivated. During the last incident on Saturday, a member of an ethnic minority was targeted in her car." Opposition leader Binyamin Netanyahu, responding to both the stoning attack and the mourning tent pitched in east Jerusalem by the family of Ala Abu Dnaim, the terrorist who shot dead eight students at the city's Merkaz Harav Yeshiva on Thursday, said it was time for "Israeli Arab leaders to take a side. They must condemn the terrorism and the rocks, and show that they are on the side of the State of Israel." "Israel cannot afford to have an enemy at home," Netanyahu said. But Galilee police spokesman Eran Shaked, whose district has seen around 10 rock throwing incidents in the past 10 days, said Netanyahu's attempt to paint the attacks with nationalistic colors was unfounded. "In the Galilee, this has been going on for a long time. It's not a new phenomenon," Shaked said. "I would not call this an escalation." One recent rock-thrower in Acre was Jewish, Shaked said. "Aside from this incident, assuming we are talking about minorities who are doing this, they can't know if the vehicle they're throwing the rock at is Arab or Jewish. Therefore, to attribute nationalistic motives to them is a judgmental approach, not one that is fact-based," he said. "I don't support it, and I can't say whether it's true or not." Shaked said it was not the police's "job to interpret these events, we deal with facts. We try to prevent this as much as possible, although it's very hard to do that with 100 kilometers of highway running through our district. It's also very difficult to track the rock-throwers down." Galilee police arrested and then released two suspected rock throwers over the weekend, because they did not match descriptions, Shaked said.