First targeted killing by Israel this year and death of hardline settler likely to frustrate US efforts at restarting peace talks

Violence erupted Tuesday in both Gaza and the West Bank, with the assassination by Israel of a militant bomb-maker and the killing of a Jewish settler, actions which are likely to complicate a drive by the United States to bring both sides back to negotiations after a four-year impasse.

The targeted killing of Hitham Masshal, 24, described by Israel as a "global jihad-affiliated terrorist", in an airstrike in northern Gaza risked fracturing the ceasefire in place since the end of the eight-day conflict last November. It was the first assassination since Egypt brokered a truce to end last year's violence.

In the West Bank, clashes followed the stabbing to death of Eviatar Borovzky, 30, as he waited for a bus. Large numbers of Israeli security forces were deployed amid fears that the killing could trigger widespread confrontations.

The renewed violence is likely to dismay the US secretary of state, John Kerry, who is on a drive to get the Israelis and Palestinians back to the negotiating table after four years without direct talks. Kerry has visited the region three times in recent weeks in an effort to broker confidence-building measures, which are seen as a necessary precursor to renewed negotiations.

The Israeli Defence Forces (IDF) claimed Masshal had taken part in a recent rocket attack on the Israeli Red Sea resort of Eilat, saying he had "acted in different jihad Salafi terror organisations and over the past few years has been a key terror figure".

He was targeted by an Israeli warplane while riding a motorcycle at about 10am. "A direct hit was confirmed," said a statement from the IDF. Video footage showed blood and the destroyed vehicle at the scene of the strike. A second man, riding with Masshal, was reported to be injured.

The IDF statement said that Masshal had worked with "all of the terror organisations in the Gaza Strip. He manufactured, improved and traded different types of ammunition, specialising in rockets and explosive devices, which he sold to terror organisations". Reports from Gaza suggested that Masshal was an explosives expert for hire, rather than ideologically motivated.

The attack on Eilat on 17 April involved two rockets fired from the Egyptian Sinai. One, which landed in a residential area, caused minor damage; the other landed on open ground. At the time, the Israeli prime minister, Binyamin Netanyahu, said the attack was the work of "a terrorist cell that left Gaza and used Sinai in order to attack an Israeli city" and warned that Israel "will exact a price for this".

On Tuesday Netanyahu said: "Today we struck at one of those involved in the criminal firing of rockets at Eilat. I said that we would not ignore this; our action is in continuation of our policy. We will not accept the sporadic firing of rockets from either the Gaza Strip or Sinai. We will act, and are acting, in order to defend Israeli citizens."

Israeli forces have carried out two airstrikes since the end of November's conflict, both in response to rocket fire.

Fawzi Barhoum, a Hamas spokesman, the Islamist organisation that controls Gaza, called the targeted killing "dangerous and unjustified", adding that the strike violated the ceasefire agreement.

Hamas has observed the ceasefire, blaming intermittent rocket fire into Israel in the past two months on small ultra-extreme organisations which it is trying to rein in.

"There are no more than 10 guys involved [in firing rockets from Gaza]," Ihab al-Ghusain, head of the Hamas government's media office, told the Guardian in Gaza City this week. "Nobody accepts people doing things against the [ceasefire] agreement."

There are widespread fears in Gaza that further military confrontation is inevitable.

In the West Bank, clashes between militant settlers and Israeli security forces in the West Bank were reported following the attack on Borovzky. Two Palestinian school buses were stoned by settlers, while other settlers set fire to tyres and olive groves, a Palestinian official, Ghassan Daghlas, told the news agency Ma'an. Settlers were planning protests for later in the day, around the time Borovzky's funeral was expected.

Borovzky, a part-time security guard and a father of five children at the hardline settlement of Yitzhar, near Nablus, was attacked early Tuesday morning at a bus stop at the Tapuach Junction, a tense spot where settlers congregate to catch buses or hitch-hike. Palestinian services, or shared taxis, are banned from stopping at the junction.

The Israeli was reportedly stabbed three times, at least once in the chest, and died of his wounds at the scene of the attack. His assailant snatched the settler's gun and shot at nearby border police. They returned fire, wounding the Palestinian, who was detained and taken to hospital in Israel.

Yariv Levin, chairman of Israel's governing coalition, said the attack was "the Palestinian response to John Kerry's new peace initiatives". Avi Roeh, of the Yesha Council, which represent settlers, said that "history proves that talk of concessions is the biggest producer of terror attacks".

Borovzky is the first Israeli to be killed by Palestinians in the West Bank since September 2011, when Asher Palmer, 25, and his baby son died after a rock was thrown at their car. Six months earlier, five members of the Fogel family were stabbed to death in their home in the settlement of Itamar.

2012 was the first year that no Israelis were killed in the West Bank, according to the Israeli internal security service, Shin Bet. Since the beginning of this year, nine Palestinians have been killed by Israeli forces in the West Bank. Israeli security analysts have warned repeatedly of mounting tension in the area which, they say, could lead to renewed violence.

Meanwhile, about 2,000 Israeli military reservists have been called up for a 48-hour exercise on the border with Lebanon.