EU foreign ministers, the Palestinian Authority, many Arab countries and the Vatican have condemned Israel's assassination of Sheikh Ahmed Yassin, founder of the militant group, Hamas.
An estimated 200,000 took to the streets to mark the funeral of the 67-year-old paraplegic cleric in Gaza this afternoon.
The Holy See said the Israeli helicopter strike on Yassin could not be justified in any state of law.
Sheikh Yassin was killed along with seven other Palestinians in a pre-dawn strike near a mosque.
The Israeli Army said Yassin was responsible for numerous terror attacks which had killed foreign and Israeli civilians.
The armed wing of Hamas has said it wants to kill hundreds of Israelis in revenge attacks. Hamas has said Israel has opened the gates of hell.
Protests follow killing
Thousands of Palestinians have been demonstrating in Gaza City following the killing.
Sheikh Yassin's assassination has been condemned by Britain and France, as well as by the Palestinian Authority and many Arab countries.
Speaking in Brussels before a meeting to discuss counter-terrorism, Britain's Foreign Secretary Jack Straw described the killing as unlawful and unjustified.
The EU's Foreign Policy Chief, Javier Solana, said the killing was very bad news for the Middle East peace process.
However, speaking at a news conference in Jerusalem, the Israeli Prime Minister, Ariel Sharon, congratulated his country's security forces and said the war on terrorism would continue.
US denies assassination involvement
Meanwhile, the US has strongly denied any involvement in the assassination.
The White House National Security Adviser, Condoleezza Rice, said the US did not have advance warning of the assassination.
Following the Sheikh's killing, there were reports of a bomb attack at the Israel/Gaza border crossing at Erez.
In another incident, it was reported that a Palestinian journalist was shot dead by Israeli troops in a refugee camp on the outskirts of Nablus while covering protests.
