Hamas says it launched rockets and mortars in response to Israeli air strikes, which also wounded 30 Palestinians.

At least two teenagers in the Gaza Strip have been killed by Israeli air raids, according to Palestinian health officials, as Israel carried out the largest daylight attack on the besieged enclave since the 2014 war.

Amir al-Nimra, 15, and Luay Kaheel, 16, died of their wounds on Saturday shortly after an air strike targeted al-Kateeba, an area in western Gaza, the health ministry said.

Twelve others were wounded by the attack.

The al-Kateeba square is adjacent to a park frequently visited by families over the weekend, especially during the summer months, witnesses told Al Jazeera.

“That’s why so many civilians have been hurt in the latest strike,” Maram Humaid, a journalist in Gaza, said.

In a Twitter post, the Israeli military confirmed it targeted a “high-rise building” and said it had “warned” residents to evacuate prior to the attack.

Witnesses told Al Jazeera that the two teenagers who lost their lives were playing on the roof of the semi-abandoned building and described a scene where “there was glass everywhere”.

At least 30 people have been wounded in the raids, which targeted several neighbourhoods in Gaza.

Following the attack on al-Kateeba, a ceasefire agreement was reached through international and regional mediation efforts, Palestinian officials said on Saturday.

In a Twitter post, Hamas, the group governing the Gaza Strip, said the efforts of “several parties” including neighbouring Egypt succeeded in implementing a lasting ceasefire.

There has been no immediate confirmation from the Israeli side.

Waleed al-Nimra mourns the death of his 15-year-old brother Amir al-Nimra [Hosam Salem/Al Jazeera]

Earlier in the day, it said it attacked several Hamas positions in the Gaza Strip, as dozens rockets and mortars were fired towards Israel from the besieged enclave.

“The Israeli army says over 90 mortars and rockets have been fired over the last 24 hours, most of them causing no damage. Some rockets hit a synagogue, also a car and we understand four Israelis were lightly injured,” said Al Jazeera’s Stefanie Dekker, reporting from Jerusalem.

“This does show you how severe this escalation has been, certainly the most severe since 2014.”

The Israeli army said its fighter jets targeted “complexes used to prepare arson terror attacks and a Hamas terror training facility”. It also said it struck two Hamas tunnels, one in southern Gaza and one in the north, as well as other infrastructure across the besieged coastal territory.

Hamas spokesman Fawzi Barhoum said the group was responsible for the mortar fire on Israel and that they were carried out “in response to the Israeli air strikes”.

“The protection and the defence of our people is a national duty and a strategic choice,” Barhoum said.

Incendiary kites from Gaza that have burned large tracts of farmland in Israeli border areas have increased public pressure on Israeli Prime Minister Benjamin Netanyahu for a stronger armed response.

Great March of Return

The escalation came just hours after a 15-year-old Palestinian was shot dead by Israeli forces at protests in the Gaza Strip near the fence with Israel and scores were wounded.

A 20-year-old died on Saturday of gunshot wounds.

Hundreds of protesters had amassed near the border fence between Israel and the Gaza Strip on Friday to commemorate more than 100 days since the start of the Great March of Return mass rallies.

Since the protests began on March 30, at least 138 Palestinians have been killed by Israeli forces and more than 160,000 have been wounded.

Its main message is to call for the right of return for Palestinian refugees and their descendants who were violently expelled from their homes in the territories taken over by Israel during the 1948 war, known to Arabs as the Nakba.

A wounded Palestinian man inside al-Shifa hospital in Gaza [Hosam Salem/Al Jazeera]

‘Open-air prison’

The Gaza Strip is but one of the focal points in the Israeli-Palestinian conflict.

More than two million Palestinians are packed into the Gaza Strip, a territory the size of the US city of Detroit – about 360sq km – which has been described as “the world’s largest open-air prison”.

Israel withdrew its troops and settlers from Gaza in 2005 but, citing security concerns, maintains tight control of its land and sea borders, which has reduced its economy to a state of collapse.

Egypt also restricts movement in and out of Gaza on its border.

Peace talks between Israel and the Palestinians have been stalled since 2014 and Israeli settlements have expanded in occupied territory Palestinians intended to become part of their eventual state.

Gaza experienced its most significant conflict in 2014, when at least 2,251 Palestinians, most of whom were civilians, were killed. At least 66 Israeli soldiers and six civilians were also killed.

Additional reporting by Hosam Salem in Gaza