Israeli troops shot dead two Palestinians during Friday protests at the Gaza-Israel border, the health ministry in Gaza said.
The breach comes amid another round of violent riots along the Israeli-Gaza border that have occurred nearly weekly for the past several months. It marked the first time all members of the political bureau got together in Gaza, Hamas has said.
Israel and Hamas have fought three wars since 2008.
Saleh al Arouri's arrival in Gaza has been interpreted in Israeli and Palestinian media as "relevant to negotiations through third parties for a long-term agreement between Hamas and Israel."
Israel's military says a tank fired at a Hamas military post in Gaza after Palestinians briefly crossed the frontier and threw bombs.
According to Israeli daily Yedioth Ahronoth, Israeli Defense Minister Avigdor Lieberman took the decision in ostensible retaliation for ongoing incendiary balloon attacks by Palestinian activists in Gaza.
The military said it sustained no casualties in the incident.
Israeli Prime Minister Benjamin Netanyahu has canceled a South American trip planned for next week due to the situation around the Gaza Strip, an Israeli official said on Thursday, as United Nations ceasefire talks pressed on.
Two farmers have also been killed in proximity to the fence since 2014 and at least 26 have been injured, excluding the over 155 killed and 17,000 injured by Israeli gunfire along the border fence in the March of Return demonstrations that started on March 30.
Some 8,000 Gazans rioted at five different points along the Gaza border, hurling firebombs (Molotov cocktails), rocks and live fireworks at IDF soldiers, "attempting to sabotage security infrastructure", the IDF spokesperson said.
In another development, a boat carrying activists challenging Israel's naval blockade of Gaza is approaching the territory, said the Freedom Flotilla Coalition, an umbrella group for pro-Palestinian and Islamic charities from around the world.
Abdul-Latif Qanou, Hamas spokesman in Gaza, said in a statement that the marches have become very close to achieving its goals.
The deal would purportedly include the improvement of living conditions inside Gaza, in addition to a sea port and an airport in Egypt.
Spokesperson of the Israeli army said in a statement that naval forces located and intercepted a Gaza-bound ship and steered it to the Ashdod seaport.
"The ship was monitored and was intercepted in accordance with global law", the Israeli military claimed.