"There will be targeted killings and other measures. The timing depends on intelligence," the source said, a day after the bombers from the resistance movements Hamas and al-Aqsa Martyrs Brigades struck at Ashdod port, killing 10 people. "The targets will be from the top down."
The source told Reuters he could not rule out an attack on Hamas's spiritual leader Shaikh Ahmad Yasin.
The wheelchair-bound cleric was slightly wounded in an Israeli air strike in Gaza in September as he met other senior Hamas figures.
Israel also tried to assassinate Mahmud al-Zahhar, another Hamas leader, in September. His son and a bodyguard were killed in an air attack on his home.
An Israeli air attack killed Ismail Abu Shanab, a Hamas leader, in Gaza in August.
"There will be targeted killings and other measures. The timing depends on intelligence"
Israeli security source
Last June Israel went after top Hamas official, Abd al-Aziz al-Rantisi in a helicopter attack on his car in Gaza. Al-Rantisi was wounded in the strike.
On Monday Israeli occupation forces seized five Palestinian resistance fighters in the West Bank as workers from the Gaza Strip were prevented from entering Israel in the aftermath of Sunday's attack.
One man taken away from the Ram Allah area was a member of Hamas. The other four were picked up from around Nablus.
Palestinians prevented from
passing through Eretz crossing
The Israeli authorities also closed off from midnight the Eretz border crossing to Palestinians from Gaza, thousands of whom cross every day to work in Israel.
The two bombers both came from Jabaliya refugee camp in the northern Gaza Strip.
"This measure has been taken following the double suicide attack," a military spokesman said.
Palestinians would still be allowed to work in a cross-border industrial zone at Eretz.
Israeli police were placed on a maximum state of alert after the attacks, with numbers beefed up around strategic sites such as ports, Ben Gurion international airport and the border between Israel and the West Bank.
Israeli occupation troops also raided the refugee camps of Balata and Tulkaram in the northern West Bank on Monday where they took over civilian houses as observation posts, Palestinian security sources said.
Soldiers seized four houses in Tulkaram and two in Nablus's Balata camp, the sources said.
Israeli troops seized four
Palestinian homes in raid
The house of a wanted resistance fighter was also briefly searched in Balata.
Three kilometres west of Nablus in the town of Zawata, the army arrested four Palestinian men. The sources said they were not wanted by the Israeli authorities.
Israeli military sources confirmed the fact a house had been searched in Balata.
"This was routine activity, there was a search. The forces have already left," they said.
They also said "an activity is going on in Tulkaram, it should not last too long," without elaborating.