Acting Israeli Prime Minister Ehud Olmert, reacting to a recent upsurge in Palestinian militant attacks, vowed Thursday to use "an iron fist" against acts of terror and said no restrictions would be placed on security forces.

Olmert spoke after a rash of shooting and stabbing attacks claimed the life of one Israeli civilian and injured five. In the latest attack, an Israeli man was stabbed in the neck at an Israeli factory in northern Jerusalem on Thursday.

Additionally, militants in Palestinian-controlled Gaza have been firing homemade rockets at southern Israel, unsettling residents but causing few injuries.

"We will use an iron first against any attempt to renew terror activity anywhere," Olmert told reporters in Jerusalem. "There are no restraints on security forces to use any means necessary to stop terror attacks."

A day earlier, at a campaign stop ahead of March 28 Israeli elections, Olmert said Israel would pursue all opportunities for peace but would relentlessly fight Palestinian terrorism.

"No one who fires off a Qassam rocket will have a moment's rest, because we shall seek him out everywhere, track him everywhere, reach him and make sure he is not able to do it," Olmert said.

In recent weeks, Israel has stepped up arrest raids in the West Bank and carried out pinpointed killings of Gaza militants it says were involved in planning or carrying out attacks. It denied involvement, however, in the car blast Wednesday in Gaza City that killed Islamic Jihad's top military commander in Gaza, Khaled Dahdouh.

Olmert also told reporters that Israel was intensifying its campaign against the Al Qaeda terror network.

"There are, of course, attempts by terror elements, including international ones, to extend their reach in areas adjacent to us," Olmert said.

"We are systematically intensifying our war," he said, adding that "all restraints have been lifted on security forces where preventing and thwarting (terror) is concerned."

Olmert spoke in response to Palestinian leader Mahmoud Abbas' acknowledgment in a published interview that Al Qaeda has infiltrated the Gaza Strip and West Bank.

"We have signs of an Al Qaeda presence in the West Bank and Gaza," Abbas said to the Arabic-language Al Hayat newspaper, which is published in London.

Palestinian security forces haven't captured any Al Qaeda operatives, he added.

Abbas said he had not expected the group would succeed in setting up operations in the Palestinian areas.

"The infiltration of Al Qaeda can ruin the whole region," he said.

Israel has cautioned that Al Qaeda was operating in the Gaza Strip and arrested a Palestinian allegedly working with the group.

Al Qaeda leader Usama bin Laden has repeatedly cited Israel as a target, and the Palestinian cause as one of the reasons for the network's attacks.

Meanwhile, Israel said security considerations were behind its decision to keep the Gaza Strip's main cargo crossing closed Thursday, counter to expectations.

The Karni passage has been closed since an explosion there Feb. 21 amid Israeli concerns that Palestinian militants were planning attacks there — concerns Palestinians say are unjustified. The crossing has been closed for a total of five weeks this year, causing economic hardships.

Palestinian officials said Wednesday that they had been informed by their Israeli counterparts that Karni would be opened Thursday, and Israeli military sources had said that was the plan.

But Israel informed the Palestinians Wednesday night that Karni would not reopen because Palestinian militants continued to fire rockets toward Israeli points in the area, said Salim Abu Safiyeh, director-general of the Palestinian Border Authority.

Palestinian militants frequently fire the homemade rockets toward Israel from Gaza, but they rarely cause any casualties.

"The continued closure is causing humanitarian and economic harm to the Palestinian people, and threatening a real shortage in food supplies," Abu Safiyeh said.

The Israeli Defense Ministry said Defense Minister Shaul Mofaz would make a decision on Karni later Thursday.

The news Wednesday that the passage would open prompted Palestinian farmers to cancel plans to dump hundreds of tons of produce that has nearly spoiled while waiting at the crossing to be exported to Israel and Europe.