JERUSALEM — Israeli naval forces shot and killed four men wearing wet suits in the waters off the coast of Gaza today, and a militant group said they were members of its marine unit training for a mission.

The attack was the latest escalation in tensions over the 3-year-old blockade of Gaza. It came a week after Israel raided a Gaza-bound flotilla carrying humanitarian supplies and hundreds of activists protesting the closure of the Hamas-ruled Palestinian territory. Israeli soldiers killed nine activists in a clash on one of the flotilla boats, bringing fierce international condemnation and new pressure to ease the blockade.

Vice President Joe Biden said today the U.S. is closely consulting with Egypt and other allies to find new ways to "address the humanitarian, economic, security, and political aspects of the situation in Gaza." He spoke in the Egyptian Red Sea resort of Sharm El-Sheikh after meeting Egyptian President Hosni Mubarak.

The closure has been in place since 2007, when the Islamic militant Hamas seized the territory and it has kept out all but basic humanitarian goods. Israel and the West consider Hamas a terror group responsible for firing thousands of rockets at Israel and carrying out hundreds of attacks, including suicide bombings. Hamas does not recognize Israel's right to exist.

Israel hoped the blockade would weaken Hamas, prevent the entry of weapons and bring pressure for the release of an Israeli soldier captured in 2006, but those objectives have yet to be achieved.

The latest clash took place early today. The Israeli military said a naval force spotted the Palestinians in the waters off Gaza and opened fire. It claimed the forces had prevented an attack on Israeli targets.

The Palestinian militant group Al-Aqsa Martyrs' Brigades said the four killed were members of its marine unit who were training in Gaza's waters. Al-Aqsa, a violent offshoot of Palestinian President Mahmoud Abbas' Fatah faction, made the claim in a text message sent to reporters.