(CNN) -- An Israeli patrol boat struck a boat carrying medical volunteers and supplies to Gaza early Tuesday as it attempted to intercept the vessel in the Mediterranean Sea, witnesses and Israeli officials said.
CNN correspondent Karl Penhaul was aboard the 60-foot, Gibraltar-registered pleasure boat Dignity when the contact occurred. When the boat later docked in the Lebanese port city of Tyre, severe damage was visible to the forward port side of the boat, and the front left window and part of the roof had collapsed.
The Dignity was carrying crew and 16 passengers -- physicians from Britain, Germany and Cyprus and human rights activists, including former U.S. Rep. Cynthia McKinney -- who were trying to reach Gaza through an Israeli blockade of the territory.
The captain of the Dignity said the Israelis broadcast a radio message accusing the vessel of being involved in terrorist activity. But Israeli Foreign Ministry spokesman Yigal Palmor denied that and said the radio message simply warned the vessel not to proceed to Gaza because it is a closed military area.
Palmor said there was no response to the radio message, and the vessel then tried to out-maneuver the Israeli patrol boat, leading to the collision.
Penhaul said at least two Israeli patrol boats had shadowed the Dignity for about half an hour before the collision, moving around the vessel on all sides. One of the patrol boats then shined its spotlight on the Dignity while the other, with its lights off, "very severely rammed" the boat.
The captain of the Dignity told Penhaul he received no prior warning. Only after the collision did the Israelis come on the radio to say they struck the boat because they believed it was involved in terrorist activities.
The captain and crew said their vessel was struck intentionally, Penhaul said, but Palmor called those allegations "absurd."
"There is no intention on the part of the Israeli navy to ram anybody," Palmor said.
"I would call it ramming. Let's just call it as it is," McKinney said. "Our boat was rammed three times, twice in the front and one on the side."
"Our mission was a peaceful mission to deliver medical supplies and our mission was thwarted by the Israelis -- the aggressiveness of the Israeli military," she said.
The incident occurred in international waters about 90 miles off Gaza. Israel controls the waters off Gaza's coast and routinely blocks ships from coming into the Palestinian territory as part of an ongoing blockade that also applies to the Israel-Gaza border. Human rights groups have expressed concern about the blockade on Gaza, which has restricted the delivery of emergency aid and fuel supplies.
The collision was so severe, Penhaul said, that the passengers were ordered to put on their life vests and be ready to get in lifeboats. The Dignity began taking on water, but the crew managed to pump it out of the hull long enough for the boat to reach shore.
Palmor said the vessel refused assistance after the incident.
The boat was carrying boxes of relief supplies, volunteers and journalists to Gaza, the Palestinian territory now subject to an intense Israeli bombing campaign.
Israel launched airstrikes against Gaza on Saturday in what Defense Minister Ehud Barak called an "all-out war" against the Palestinian militant group Hamas, which has ruled the territory since 2007.
The Palestinian death toll has topped 375, most of them Hamas militants, Palestinian medical sources said Tuesday. At least 60 civilians have been killed in Gaza, U.N. officials said.
Hamas has responded with volleys of rocket fire aimed at southern Israeli towns, which have left six Israelis dead -- five of them civilians.
Hamas has vowed to defend Gaza in the face of what it calls continued Israeli aggression. Each side blames the other for violating an Egyptian-brokered cease-fire, which formally expired December 19 but had been weakening for months.