A clash seems to be looming between Israel and the radical Islamist movement Islamic Jihad, as they abandon pledges made under a fragile ceasefire that ended the last full-scale war in the Hamas-run Gaza Strip.
Israel recently targeted two of the group's terrorists for firing rockets at it, and Prime Minister Binyamin Netanyahu promised to teach Gaza-based terrorists a "lesson" for repeated breaches of the ceasefire.
Islamic Jihad has in turn threatened to take its war to Israel, both through suicide bombings in major Israeli cities and by fomenting violent unrest in Judea and Samaria - against both Israeli and Palestinian Authority security forces.
Islamic Jihad carried out scores of deadly suicide bombings against Israeli civilians during the "Second Intifada" between 2000 and 2005.
In the latest violence, Islamic Jihad said Israel killed one of its operatives, Ahmad al-Zaaneen (who was also associated with the Popular Front for the Liberation of Palestine) and his cousin in an air strike in the northern Gaza Strip Wednesday.
Israel said Zaaneen was behind rocket attacks on the Jewish state and an "immediate" danger to Israeli civilians.
In response, Islamic Jihad promised to continue targeting Jewish civilians, declaring "the blood of our martyrs will not have been shed in vain."
Following the airstrike, Netanyahu promised Gaza-based terrorist groups, including the enclave's Islamist rulers Hamas, that they would learn a lesson "very soon" if rockets continued to be fired, referring to Israel's policy of retaliating "forcefully."
The security correspondent for Israel's Yediot Aharonot daily said the strikes marked a justified escalation in the face of regular breaches of the truce by terrorist groups.
"Ever since Operation Pillar of Defense (in 2012), there was an understanding with Hamas that no targeted killings would take place as long as the quiet was maintained," he wrote.
"The moment it became clear that Hamas was losing control of the Gaza Strip - this weapon was again pulled out."
"Targeted killings are the most effective means of dissuasion against the organizers of terrorism, especially in the Gaza Strip where the Israeli army cannot go in and make arrests," as in Judea and Samaria.
"The decision to carry out suicide operations in Zionist cities is one that is irreversible," said Abu Ahmad, a senior commander in Islamic Jihad's Al-Quds Brigades.
"The operations will put pressure on the Palestinian leadership, but will also deter the enemy, and we're continuing to try to carry them out," he told AFP.
"We have a high level of weaponry with which to strike deep in the Zionist entity and send messages threatening it."
It is not clear, however, how the threats will change the situation on the ground, as the Iranian-sponsored Islamic Jihad has already been upping its activity in an attempt to target Israelis as negotiations between Israel and the Palestinian Authority continue.
On December 22, a bomb exploded on a bus in the Israeli coastal city of Bat Yam, near Tel Aviv.
No Gaza group claimed responsibility, but Israel's Shin Bet internal security service arrested four men in the PA-controlled town of Bethlehem, saying they were an Islamic Jihad cell behind the attack.
Meanwhile, Islamic Jihad spokesman Dawud Shihab told AFP the group would incite Palestinian Arabs in Judea and Samaria to violently "confront" Israeli security forces.
It "will rouse the masses and prepare them for the next confrontation with the occupation, and for the outbreak of a new intifada.
"There will be an explosion in the face of the occupation in the West Bank, because of the failure of the PA and Israel's monstrousness," he said.
But various Palestinian Arab factions are still divided and mired in internal squabbles.
Like Hamas, Islamic Jihad opposes the talks, and sees an escalation in Judea and Samaria as an effective way of undermining the PA's rule there, and thus its legitimacy in the talks.
Gaza groups also accuse the PA of colluding with Israel in the arrest of terrorists in Judea-Samaria, although it publicly bemoans Israel's lack of consultation with it on joint security efforts and insists it does not unjustly target Palestinian Arabs.
Even within Gaza, relations are complex. Islamic Jihad - inspired by Iran's 1979 revolution and formed the following year - sometimes cooperates and is sometimes at odds with the Muslim Brotherhood-allied Hamas, formed in the late 1980s.
The death of an Al-Quds Brigades commander from wounds sustained during a Hamas police raid on his house in June caused a temporary spat between the groups, before they publicly patched up their differences.
Islamic Jihad claims to have 8,000 fighters in its military wing, making it the second largest armed group in Gaza behind Hamas.
Unlike smaller Salafist factions, Islamic Jihad has so far respected an Egypt-brokered truce between Hamas and Israel that ended the 2012 conflict.