JERUSALEM  Israel faced rising international pressure on Tuesday to ease its blockade of Gaza, as the United Nations Security Council called its approach to isolating the coastal strip “not sustainable” and pro-Palestinian groups planned fresh attempts to test the closing of sea lanes around the Hamas-controlled territory.

A day after an Israel military raid on an international flotilla trying to breach the blockade left nine foreign activists dead, Egypt, an important partner for Israel in keeping tight control over the flow of goods into the territory, said it would open the land border with Gaza for humanitarian purposes.

Israel’s relations with Turkey, once relatively close, also came under heavy strain. Prime Minister Recep Tayyip Erdogan of Turkey called the raid on the Turkish ship, which killed at least four Turkish citizens, a “bloody massacre” and said Israel should immediately end “the inhumane embargo on Gaza.”

At the same time, the volatile Israel-Gaza border seemed to be heating up. Israeli soldiers killed two gunmen from the Islamic Jihad who had infiltrated Israel early Tuesday. Later in the day, the Israeli air force struck a group of militants in northern Gaza who were preparing to fire rockets at Israel, killing three.