Mourners gathered in Qatar’s capital, Doha, Friday for the funeral of Hamas leader Ismail Haniyeh, who was killed Wednesday in Tehran in an attack blamed on Israel that has raised regional tensions and the threat of a wider Middle East conflict.

Thousands of people were in attendance for the service at the Imam Muhammad ibn Abdul Wahhab Mosque, where Haniyeh’s casket and those of his bodyguards were draped in Palestinian flags. Following the service at the mosque, the caskets were taken for burial in Lusail, north of Doha.

The death of Haniyeh has triggered calls for revenge from both Iran and Hamas, both of which blame Israel for his death. Haniyeh had been in Tehran for the inauguration of Iran’s new President Masoud Pezeshkian.

Israel has not confirmed nor denied having a role in Haniyah’s death.

Haniyeh had been the Hamas political chief, and he was playing a key role in mediated talks aimed at reaching an agreement that would end nearly 10 months of war between Hamas and Israel in the Gaza Strip, as well as release hostages taken during Hamas’ October 7 terror attack on Israel.

The future of those talks is now in question. U.S. President Joe Biden, asked Thursday at the White House if the assassination of Haniyeh ruins the chance for a cease-fire, replied simply, “It’s not helped.” He was also asked if he believed Iran would retaliate but would not comment.

Fears of retaliation against Israel have raised tensions throughout the region.

Reuters reports that Dutch airline KLM has announced it will cancel all of its flights to and from Tel Aviv until October 26 because of the situation. That follows similar decisions by Lufthansa, Delta, United and other airlines in recent days.

U.S. Deputy Pentagon Press Secretary Sabrina Singh told reporters Friday that U.S. Defense Secretary Lloyd Austin offered Israel’s defense minister support that is “ironclad and ongoing” to help defend Israel from Iran. Singh said they hope to send a message of deterrence to Iran.

Israel said Thursday it killed Hamas military chief Muhammad Deif, believed to be the main planner of the shock October 7 Hamas attack on Israel, in the southern Gaza city of Khan Younis in mid-July.

Israeli Defense Minister Yoav Gallant called Deif the “Osama bin Laden of Gaza,” referring to the mastermind of the 2001 al-Qaida terrorist attacks in the United States that killed nearly 3,000 people.

Gallant said the killing of Deif on July 13 “is a significant milestone in the process of dismantling Hamas as a military and governing authority in Gaza, and in the achievement of the goals of this war.”

The Israeli military said in a statement that it concluded Deif was dead based on an intelligence assessment but did not offer further details. Israel had targeted him in an attack that killed at least 90 people, but Deif’s fate was unknown. Hamas has not confirmed or denied his death.

Gallant said the July operation “was conducted precisely and professionally” by the Israel Defense Forces and the Israel Security Agency. “This operation reflects the fact that Hamas is disintegrating, and that Hamas terrorists may either surrender or they will be eliminated,” Gallant said.

Deif escaped several Israeli assassination attempts, including when Israel bombed his home in 2014, killing his wife and infant son.

As the attack on Israel began last October, Deif released a recorded speech saying Hamas had launched the operation so that “the enemy will understand that the time of their rampaging without accountability has ended.”

Deif was the third significant anti-Israel militant killed in attacks in three countries in recent days.

On Tuesday, an Israeli airstrike on a Hezbollah building in Beirut killed Fouad Shukur, the Hezbollah commander Israel said was responsible for an airstrike on a football field in the Golan Heights last weekend that killed 12 children and teenagers.

Hamas militants killed about 1,200 people and captured about 250 hostages in their October 7 terror attack on Israel that sparked the war. Israel says it believes Hamas is still holding 116 hostages, including 42 that the military says are dead.

Israel has since responded with an air and land assault on Hamas-governed Gaza, which both sides agree has killed more than 39,480 people. Israel says the majority of the dead are combatants. The Hamas-run Health Ministry says the majority of them are women and children, but it does not estimate how many of the dead are combatants.

Nearly three-quarters of Gaza’s 2.3 million population is displaced, and nearly the entire population is at risk of famine, according to the United Nations.

Some information in this report came from The Associated Press and Reuters.