With tensions high along the Gaza border, Israel said its aircraft attacked 10 sites in the Palestinian enclave yesterday in response to persistent rocket strikes on southern Israeli towns.
But Prime Minister Benjamin Netanyahu signalled broader Israeli action was not imminent.
The security source gave no details about the suspects arrested in the investigation into the abduction and killing of 16-year-old Mohammed Abu Khudair, other than to say they were Jewish and police saw "nationalist motives" in the case.
The teenager's burnt body was discovered in a Jerusalem forest on Wednesday. Palestinians believe he was the victim of far-right Jews avenging the kidnap-killing of three Israeli teenagers who disappeared while hitchhiking in the occupied West Bank on June 12 and whose bodies were found on Monday.
Israel blames the deaths of Naftali Fraenkel and Gil-Ad Shaer, both 16, and 19-year-old Eyal Yifrah, on Hamas. The Gaza flare-up began in mid-June during Israel's search for the teenagers in the West Bank and its arrests of Hamas members.
Hamas has neither confirmed nor denied involvement in the killings. In remarks to his cabinet yesterday, Mr Netanyahu pledged "to do whatever is necessary" to restore quiet to southern Israeli communities that have come under rocket attack from the Gaza Strip, where Hamas is the dominant force.
But he also cautioned against any rush toward wider confrontation with the group, whose arsenal includes long-range rockets that can reach Israel's heartland and its business capital Tel Aviv.
Mr Netanyahu told his cabinet: "Experience has shown that during moments like these, one must act in a level-headed and responsible manner and not hastily."
Israel beefed up ground forces along the Gaza frontier on Thursday, a deployment widely seen as sending a message to Palestinian militant groups that an invasion was an option if rocket fire did not stop.
Egypt, a bordering country, has been trying to mediate a truce.
However, in a move that could harden militants' resolve to confront Israel, the military said it cut the fishing zone for Palestinian fishing boats off Gaza from six to three nautical miles.
East Jerusalem and other flashpoint Arab communities were quiet yesterday after protesters angered by Abu Khudair's death clashed with police late on Saturday.
An autopsy attended by a Palestinian pathologist showed soot in Abu Khudair's lungs, indicating he was still alive when he was set on fire, the Palestinian attorney general said.
Meanwhile, Palestinian-American Tariq Khdeir, 15, a cousin of the dead Palestinian teenager, was arrested by Israeli border policemen, who his family said beat him severely, during a protest on Thursday in East Jerusalem.
An Israeli court yesterday ordered the teenager to be released from jail and placed under house arrest for nine days. His mother said the family planned to return to Tampa, Florida, on July 16.
The US has called for an investigation and Israel's Justice Ministry said the police internal affairs office was looking into the incident.