A Lebanese boy was killed early Tuesday in an explosion in a village near the border with Israel (search), hours after an Israeli soldier was killed in a cross-border shooting.

The killing of the soldier prompted Israeli officials to warn Lebanon (search) and Syria to rein in anti-Israeli militants or face an escalation in the area.

The violence signified heightened tensions between Israel and Syria (search), Lebanon's close ally, following Israel's air raid Sunday on what the Jewish state said was a Palestinian militant base deep inside Syria.

In Tuesday's violence, Lebanese security officials and residents of the southern Lebanese border village of Houla said Ali Yassin, 4, was killed and his twin brother wounded in the explosion.

It was not known whether the explosion was a falling antiaircraft shell fired from Lebanon or a projectile aimed at Israel that fell short, the Lebanese officials said.

Israel's army said at least three mortar shells were shot early Tuesday from Lebanon toward northeastern Israel. Israel Radio reported the Lebanese boy was killed when one of the shells landed short. No injuries were reported on the Israeli side.

Yassin's twin brother, Ahmed, also was wounded in the impact, one of three heard by Houla residents early Tuesday.

Within minutes of the explosion, Israeli military fighter jets and helicopter gunships flew reconnaissance missions over the border area near Houla, villagers said.

In Monday's incident, shots were fired by a sniper of the anti-Israeli militia, Hezbollah (search), toward Israeli soldiers on a routine patrol near the border with Lebanon not far from the Israeli town of Metulla, the Israeli army said. Soldiers returned fire but did not identify that any people or structures were hit, the army said.

Hezbollah, which is backed by Syria and Iran, said in a one-sentence statement faxed to The Associated Press in Beirut that it was not involved in Monday's shootings. Lebanese security officials said two cars and a house in the Lebanese village of Kfar Kila were hit by the Israeli fire but no one was injured.

An officer from the U.N. Interim Force In Lebanon, a peacekeeping force that regularly sends patrols along the Lebanese side of the border, said a U.N. water tanker truck was hit by three bullets.

The Israeli army was on high alert along its northern borders with Lebanon and Syria in light of the violence this week, Army Radio reported.

The head of Israel's northern command, Maj. Gen. Benny Gantz, warned Lebanon and Syria that a refusal to stop the Hezbollah activities would bring about Israeli retaliation.

"These actions are very dangerous for Lebanon and Syria... and can bring about a serious deterioration in the situation," said Gantz in a press conference after the soldier was killed. "Syria is responsible for what happened here, by letting the terror groups act freely."

A senior Israeli military official said on condition of anonymity that Israel was considering further retaliation against Syria, Lebanon and Hezbollah.

Yuval Steinitz, the head of the parliamentary Foreign Affairs and Defense Committee, said Monday that Israel would not hesitate to attack terrorists operating against Israel, even if they are located in Syrian or Lebanese territory.

"We need to signal to all the regimes around us, `Gentlemen, we are not interested in a war, nor an escalation into a semi-war, but if you continue to support terror, we won't have any choice,"' Steinitz told Israel Radio.

Israel withdrew from a strip of territory in south Lebanon in May 2000 after an 18-year occupation of the area in an effort to prevent cross-border attacks.

Most of the border has been relatively quiet since then.

The Israeli raid against a reputed training camp of the militant group Islamic Jihad located 15 miles northwest of Damascus on Sunday came in response to a homicide bombing by the group in Israel that killed 19 bystanders.