Israeli missiles struck a training camp for the Palestinian radical group Hamas in the Gaza Strip early Tuesday, killing at least 13 fighters and injuring about 25 other people, many critically, Palestinian hospital officials and witnesses said.

The attack occurred shortly after midnight in the Sajaiya neighborhood in the east-central part of the Gaza Strip, near the Israeli border, hospital officials said. The camp was located on an old soccer field.

The missiles struck a week after Hamas, known formally as the Islamic Resistance Movement, asserted responsibility for a double suicide bombing that killed 16 people and wounded about 100 others in the southern Israeli town of Beersheba.

That attack, in which two bombers blew up two buses within 100 yards of each other just seconds apart, shattered a months-long lull in major suicide strikes in Israel.

The Gaza attack targeted a Hamas facility that was "known as a gathering field of Hamas terrorists to be trained in the planting and activating of explosive devices," and that was used for "practicing infiltration into Israeli communities and military posts," according to a statement released by the Israeli military. People at the camp had recently been trained to kidnap Israelis, the statement added.

Witnesses said at least four missiles slammed into the training facility during an attack that lasted about two minutes. They said that no helicopters were seen during the assault, leading them to conclude that the missiles were fired by tanks.

But foreign news agencies reported that Israeli helicopters were spotted in the vicinity at the time of the strike, and a statement by the Israeli military said the attack was carried out by the air force.

The explosions lit up the skies over the Gaza Strip and rocked buildings six miles away in Gaza City. Jumaa Saqqa, a senior physician at Shifa Hospital in Gaza City, said that 13 militants were killed in the attack and that at least 25 other people were wounded, many with life-threatening injuries.

Special correspondent Islam Abdelkarim in Gaza City contributed to this report.

Of the dozens of Palestinians wounded in the Israeli attack, many had life-threatening injuries, a physician said.