JERUSALEM, Sept. 8 (Xinhua) -- Palestinian militants in northern Gaza fired a mortar into a nearby Israeli kibbutz community Wednesday morning that slammed down between kindergarten classrooms.

The shell, which caused slight damage but no casualties, failed to trigger an early-warning system meant to detect rocket fire from the Hamas-ruled area.

The structure's rooms were unoccupied at the time, although children were on their way to classes within about half an hour, local security officials said.

"We heard a loud explosion. I woke up in panic. The shell exploded about 100 meters from my house. The blast was so powerful that it set off the car alarms. It was very frightening," a report on the local Ynet news website quoted a kibbutz resident as saying.

Security officials decided to keep the kindergartens open, but instructed children and staff to remain indoors for the next few hours.

The shelling took place on the eve of Rosh Hashana, the two-day Jewish New Year.

The strike came on the heels of an uptick in mortar and Kassam rocket strikes at Israeli targets since the onset of direct negotiations between Israel and the Palestinian National Authority (PNA) began last week. Gaza militants fired a Kassam towards Israel on Saturday that hit an open field, causing no damage.

Hamas officials bitterly slammed the talks between Israeli Prime Minister Benjamin Netanyahu and PNA President Mahmoud Abbas.

Israeli security forces are on high alert for possible attacks from Gaza and the West Bank by pro-Hamas Palestinians after four Israeli civilians were killed and two wounded in two shootings last week. Hamas in Gaza has claimed responsibility for the attacks.

PNA officials said Tuesday night that they arrested two Hamas supporters from a village near Ramallah in connection with the second shooting attack, which took place near Ramallah. The PNA said, however, that they would not hand over the suspects to Israel.

PNA Prime Minister Salam Fayyad said a day earlier that his security forces arrested several hundred Hamas members since the attacks, and said security forces detained two Palestinians from Hebron in connection to the first shooting.

"The decision to carry out the attack was politically motivated and intended to embarrass the Palestinian National Authority," Fayyad told Palestinian journalists, according to The Jerusalem Post.

The Hamas, for its part, has vowed to continue attacking Israeli targets, and said they may return to suicide bombings within Israeli territories and settlements in the West Bank.

Israeli army and border police forces, as well as private security firms, have beefed up their visibility in the West Bank in an effort to assure a quiet holiday. Military jeeps and personnel are common scenes at major highway intersections and on patrols within settlement communities.

In Jerusalem, a heavy police is present in the city's Mahane Yehuda outdoor market.

Gun-toting border police officers strolled among the crowds, as Arab and Jewish workmen unpacked pallets of canned goods, fruits and vegetables. A police officer led a bomb-sniffing dog among the stalls, as last-minute shoppers thronged the covered lanes and bought groceries for holiday meals.

In an effort to reduce the chances of terror infiltrations, security forces have closed crossings between Israel and the West Bank until the end of the holiday and Sabbath, Saturday night.