United States Secretary of State Antony Blinken said on Monday he has asked Israel for any evidence of Hamas operating in a Gaza building, housing news bureaus, which was destroyed by an Israeli airstrike over the weekend, but hasn't seen any.

Blinken spoke at a news conference in Copenhagen, Denmark, as pressure is increasing on the Biden administration to ask for a ceasefire in the latest flare-up between Israel and Hamas — the Gaza Strip’s rulers.

Israel destroyed a building housing The Associated Press and Al Jazeera offices and claimed that Hamas used the building for a military intelligence office. Prime Minister Benjamin Netanyahu has called the building a “perfectly legitimate target”, and said in a televised address on Sunday that Israel passes such evidence through intelligence channels.

“Shortly after the strike we did request additional details regarding a justification for it,” Blinken said on Monday. He declined to discuss specific intelligence, saying he “will leave it to others to characterise if any information has been shared and our assessment [of] that information”.

But he said, “I have not seen any information provided.”

Blinken's comments came after United Nations Security Council diplomats and foreign ministers of Muslim states convened emergency weekend meetings to demand a stop to civilian bloodshed as Israeli warplanes carried out the deadliest single attack in nearly a week of Israeli airstrikes.

US President Joe Biden gave no signs of stepping up public pressure on Israel to agree to an immediate ceasefire despite calls from some Democrats for the Biden administration to get more involved.

His ambassador to the UN, Linda Thomas-Greenfield, told an emergency high-level meeting of the Security Council that the US was “working tirelessly through diplomatic channels” to stop the fighting.

But as battles between Israel and Gaza's Hamas rulers surge to their worst levels since 2014 and the international outcry grows, the Biden administration, determined to wrench the US foreign policy’s focus away from the Middle East and Afghanistan, has declined so far to criticise Israel's part in the fighting or send a top-level envoy to the region. Appeals by other countries show no sign of progress.

Thomas-Greenfield warned that the return to armed conflict would only put a negotiated two-state solution to the decades-old Israeli-Palestinian conflict even further out of reach. However, the US, Israel's closest ally, has so far blocked days of efforts by China, Norway and Tunisia to get the Security Council to issue a statement, including a call for the cessation of hostilities.

In Israel, Hady Amr, a deputy assistant dispatched by Blinken to try to deescalate the crisis, met with Israeli Defense Minister Benny Gantz, who thanked the US for its support.

Blinken himself headed out on an unrelated tour of Nordic countries, with no announced plans to stop in the Middle East in response to the crisis. He made calls from the plane to Egypt and other nations working to broker a ceasefire, telling Egypt that all parties should deescalate tensions and bring a halt to the violence.

Adam Schiff, the chairperson of the House Intelligence Committee, urged Biden on Sunday to step up pressure on both sides to end the current fighting and revive talks to resolve Israel's conflicts and flashpoints with the Palestinians.

“I think the administration needs to push harder on Israel and the Palestinian Authority to stop the violence, bring about a ceasefire, end these hostilities, and get back to a process of trying to resolve this long-standing conflict,” Schiff, a Democrat from California, said during a news programme, Face the Nation, aired on US television channel CBS.

And Senator Todd Young of Indiana, the senior Republican on the foreign relations subcommittee for the region, joined Connecticut Senator Chris Murphy, the subcommittee chairperson, in asking both sides to cease fire.

Biden focused on civilian deaths from Hamas rockets in a call with Netanyahu on Saturday, and a White House readout of the call made no mention of the US urging Israel to join in a ceasefire that regional countries were pushing. Thomas-Greenfield said US diplomats were engaging with Israel, Egypt and Qatar, along with the UN.

Israeli airstrikes on Gaza City flattened three buildings and killed at least 42 people on Sunday, medics said, bringing the toll since Israel opened its air and artillery battles to over 200 killed in Gaza. Some 55 children in Gaza and a 5-year-old boy in Israel were among the dead.

Netanyahu told Israelis in a televised address on Sunday that Israel wants to levy a heavy price on Hamas. That will take time, Netanyahu said, signaling the war would rage on for now.

Representatives of Muslim nations also met on Sunday to demand from to Israel halt attacks that are killing Palestinian civilians in the crowded Gaza strip.

The meeting of the 57-nation Organisation of Islamic Cooperation also saw Turkey and some others criticise a US-backed push, under which the United Arab Emirates, Bahrain and other Islamic nations signed bilateral deals with Israel to normalise their relations, stepping over the wreckage of collapsed international efforts to broker peace between Israel and the Palestinians in the long term.

The massacre of Palestinian children today follows the purported normalisation, Iranian Foreign Minister Mohammad Javad Zarif said.

At the virtual meeting of the Security Council, UN Secretary-General Antonio Guterres said the UN was actively engaging all parties for an immediate ceasefire.

Eight foreign ministers spoke at the Security Council session, reflecting the seriousness of the conflict, with almost all urging an end to the fighting.