Despite the tenuous ceasefire agreed between Israel and Palestinian militant group Hamas, Israeli warplanes targeted the Sheikh Radwan police station west of Gaza City, killing 10 officers and detainees, medics and police said.
Rescue teams were searching for more casualties at the site, said the police, who are run by Hamas in the Gaza Strip.
Another air strike hit an apartment in Gaza City killing three children and two women, according to officials at Shifa hospital in the city. Seven more were killed in a strike at a tent encampment in Khan Younis further south.
An Israeli military source said the strikes were carried out in response to an incident on Friday in which troops identified eight gunmen emerging from a tunnel in Rafah, an area in southern Gaza where Israeli forces are presently deployed under the October ceasefire agreement.
Three of the gunmen were killed by the forces and a fourth, whom the Israeli military described as a key Hamas commander in the area, was arrested.
Hamas did not comment on the incident, which the military source said constituted a violation of the ceasefire, and it blamed Israel for breaching the truce.
The strikes came before the Rafah border crossing is due to open in Gaza's southernmost city, a reminder that the death toll is still rising even as a ceasefire agreement inches forward.
All of the territory's border crossings have been closed since the start of the war and Palestinians see the Rafah crossing with Egypt as a lifeline for the tens of thousands in need of treatment outside the territory, where the majority of medical infrastructure has been destroyed.
Gaza's Health Ministry has recorded more than 500 Palestinians killed by Israeli fire since the start of the ceasefire on October 10. The ministry, which is part of the Hamas-led government, maintains detailed casualty records that are seen as generally reliable by UN agencies and independent experts.
Separately, the US government approved the sale of defence equipment to Israel worth nearly $US6.7 billion.
This includes new combat helicopters and armoured vehicles, according to the US Defence Security Cooperation Agency (DSCA).
The planned deals with Israel include 30 Apache combat helicopters and accessories for just under $US3.8 billion, 3,250 Joint Light Tactical Vehicles for $1.98 billion, accessories for armoured transport vehicles worth around $740 million and Light Utility Helicopters for around $150 million.
The US is Israel's closest ally, including in terms of military support and arms sales.
The State Department also approved the purchase by Saudi Arabia of 730 missiles for the Patriot air defence system and accessories worth an estimated $US9 billion. The DSCA said it had notified the US Congress.
The announcement of the planned arms deals came against the backdrop of increasing tensions in the Middle East.
US President Donald Trump has recently threatened Tehran several times with military strikes, including in connection with the violent crackdown on recent protests in Iran. He has also increased the US military presence in the Middle East.
Initially, no time frame was given for any of the planned arms deals.
with agencies
