A day after Israel assassinated Hamas's top commander in the Gaza Strip in a new offensive, hundreds of delegates at the conference in Sudan burst into applause and cheers as Mashaal, dressed in a suit and open-necked shirt, entered Khartoum's hangar-sized Friendship Hall.
"Khaybar, Khaybar," the crowd chanted as Meshaal shook hands with other Islamist leaders, in a reference to a battle in Arabia where the Prophet Muhammad and his followers defeated Jewish defenders in the 7th century. "The army of Muhammad has started to return."
Although most attendees were Sudanese, some came from as far as Indonesia and Senegal.
Among the delegates were the leaders of the Islamist parties in Egypt and Tunisia that have come to power through the ballot box in the wake of the Arab Spring, a regional shift towards the Islamists that has also helped embolden Hamas.
Israel has bombed targets in the Hamas-controlled Gaza Strip for two days, saying its attack is in response to escalating missile strikes from Gaza. Fifteen Palestinians and three Israelis have been killed in the flare-up.
Condemnation of the Israeli offensive has been led by Egyptian President Muhammad Mursi, from the now dominant Muslim Brotherhood.
The head of the Brotherhood, Mohamed Badie, told the conference in Khartoum: "The blood of our brothers who were martyred yesterday, just yesterday, in Palestine, in Gaza, this is what waters the tree of Islam."
Rachid Ghannouchi, leader of Tunisia's ruling Ennahda party, said: "In truth, the mother of the revolutions was the blessed Palestinian revolution."
Tunisia was the first Arab Spring country where a long serving strongman was unseated through popular protest.
Sudan's own Islamist government, headed by President Omar Hassan al-Bashir, came to power in a 1989 coup. Vice President Ali Osman Taha said Israel had no respect for international law. "This madness is a danger to international peace," he said.
Last month, Sudanese officials blamed an Israeli air strike for a blast at an arms factory in Khartoum that killed four people. Israel has not commented on the accusations, but Israeli officials have accused Sudan of funneling weapons from Iran to Hamas in Gaza.
Mashaal, who spoke just before Bashir, was greeted with chants of "Hamas, Hamas, Hamas" as he climbed onto the stage, flanked by two bearded, thickset bodyguards.
"Our enemy is your enemy," Meshaal said, interrupted several times by cheering and chanting. "Our hands are with you."
KHARTOUM, Sudan (Reuters) -- At a conference that drew a roll-call of the Islamist leaders who have gained influence in the wake of Arab Spring revolts, Hamas leader Khalid Mashaal won a noisy welcome and pledges of support on Thursday.