Israel has defended Tuesday's missile strike
An explosion in a Palestinian high school in the northern West Bank has left at least 29 teenagers injured, some seriously, Palestinian sources have said.
A Jewish militant group calling itself Revenge of the Infants allegedly claimed to have been behind the attack, but police have cast doubt on their statement.
Reports suggest that an Israeli-made grenade was found near the gates of the school and went off when students touched it.
The incident, in the West Bank village of Jabaa, near Jenin, comes as at least one man was shot dead following a raid by the Israeli army into the town of Beit Hanoun in the northern Gaza Strip.
Jenin governor Haider Irshaid blamed the school blast on Israel, saying the Israeli army had placed a bomb at the school gates.
Palestinian police who checked the scene found shrapnel and said the device was Israeli-made, with Hebrew letters on it, Mr Irshaid said.
But an Israeli army spokesman said the military rarely conducts operations in the area and Israeli army sources said there had been no units in the area at the time of the incident.
The French news agency AFP quoted an anonymous security official as doubting the Jewish militant group's claim of responsibility.
"It wouldn't be the first time the group has claimed responsibility for something they didn't do," the official said.
Also on Wednesday, at least one man was killed following an Israeli army raid into the town of Beit Hanoun in the Gaza Strip.
Israeli forces were looking for Qassam rockets and launchers after members of the Islamic militant group Hamas fired a rocket into the southern Israeli town of Sderot, Israeli radio reported. No-one was injured in the incident.
Israel has also defended the decision to carry out a missile strike which killed three Hamas militants and two civilians, including a 12-year-old boy.
The strike, which killed Saed Arabeed, a senior figure in the group's armed wing, was performed by an Israeli F-16 warplane which fired two missiles at the car Arabeed was travelling in.
We have not changed our policy on targeted operations against terrorists since the US intervention in Iraq
Israeli deputy Defence Minister Zeev Boim
Two of the other dead were Hamas militants, Ashraf al-Halabi and Imad Nassar, according to reports.
Israeli deputy Defence Minister Zeev Boim said Arabeed was "a particularly dangerous terrorist" responsible for several attacks on Israel, AFP reported.
"We have not changed our policy on targeted operations against terrorists since the US intervention in Iraq," he added.
Correspondents say the area of the raid, the Zeitoun neighbourhood in the eastern part of the city, is known as a stronghold of the Islamic militant group, Hamas.
A month ago, one of the group's founders, Ibrahim al-Maqadma, was killed in a similar attack.