"I call on everyone to do the utmost to ensure that incidents like this one are not repeated," Peres said at a campaign stop.
Foreign Minister Ehud Barak urged Labor Party activists not to be pulled into what he termed "Likud provocations."
But Likud officials said the man arrested by police as the suspected gunman was not a party activist, adding that he had merely been hired to put up posters.
The shooting was not an organized attempt "to intimidate Labor activists," said Likud spokesman Michael Stoltz.
Netanyahu called on all political parties to eject violent elements from their ranks.
Previous election campaigns in 1981 and 1984 were marred by clashes, including fistfights, between Likud and Labor supporters.
But Wednesday's incident was believed to be the first shooting linked to a political campaign.
Coming little more than six months after the assassination of Yitzhak Rabin by a religious right-wing extremist, the incident sounded alarm bells throughout Israel.
Knesset members agreed to put a discussion of the incident on the agenda for next week's scheduled special Knesset session.
The shooting occurred about 5 a.m. in Herzliya, north of Tel Aviv.
Speaking to reporters from his hospital bed, Yarusky said he had been hanging up posters when a car drove up.
Four people got out and ordered him to stop, he said. When he refused, one of them fired a gun three times, hitting him twice before the group drove away.
Herzliya police questioned two suspects Wednesday afternoon. They were looking for two other known suspects.
The lawyers of the detainees maintained that their clients had no connection to the incident and were hanging campaign posters elsewhere when the shooting occurred.