Several people have been killed in fresh Israeli airstrikes and shelling in Gaza, raising fresh concerns about the future of Israel's ceasefire agreement with Hamas.Meanwhile, US diplomats have stepped up diplomatic efforts to save the deal, Al Jazeera reported on Tuesday (October 21).The Palestinian Civil Defense said four people were killed in two separate attacks in the al-Sha'af area of ​​eastern Gaza City. The dead were returning to their homes when Israeli forces opened fire on them.The Israeli army said it had opened fire on fighters who had crossed the "yellow line" towards Shujaiyah and were "threatening" Israeli troops.The "yellow line" is a border demarcated on a map released by US President Donald Trump on October 4. Israeli troops are stationed behind the line as part of the ceasefire.However, residents of Gaza City say there is confusion about the exact location of the line. “The whole area is destroyed. We have seen the map, but we don’t know where the line is,” said Samir, 50, a resident of the Tufa neighborhood.Gaza has been rocked by attacks and violence since the U.S.-brokered ceasefire that came into effect on October 10. At least 97 Palestinians have been killed so far, according to Gaza authorities.Both sides have accused each other of violating the ceasefire agreement. Local health officials said at least 42 people were killed in Israeli air strikes on Sunday, including children.Israel claims that Hamas fighters shot and killed two of its soldiers in the Rafah area in retaliation for the attack. Hamas denies the accusations. They said they had no units active in the Israeli-controlled part of Rafah and were “not responsible” for the incidents there.A Hamas official accused Israel of “creating a pretext to restart the war.”Hamas said it had so far released 20 living Israeli prisoners and was trying to hand over the bodies of the rest. However, it said the widespread destruction in the Gaza Strip was making it difficult to complete the process.Meanwhile, Israel threatened to halt humanitarian aid deliveries to Gaza on Sunday, but later said it was upholding the ceasefire.UN spokesman Stephane Dujarric said aid deliveries had resumed, but he did not specify how much had been delivered.Al Jazeera’s Tareq Abu Azzoum reported on Monday that Israel was still blocking aid trucks from entering Gaza. “These trucks are stuck at various military checkpoints, containing various types of humanitarian aid,” he said.Azzoum added that Israeli forces carried out airstrikes on the eastern part of Khan Younis on Monday, raising fears among locals that the ceasefire could break down.In such a situation, Philippe Lazzarini, the head of the UN refugee agency UNRWA, said on the social media platform X (formerly Twitter) that the fragile ceasefire in Gaza must be preserved. At the same time, he called for “an investigation into clear violations of international humanitarian law.”