JERUSALEM (NYTIMES) - Troops ambushed four militants as they planted bombs along Israel's boundary with Syria around midnight, the Israeli military said early Monday (Aug 3), amid heightened tensions along Israel's frontiers.

The militants, whose identity or affiliation were not immediately known, were assumed to have been killed on the spot by a combination of ground and air fire, said Lieutenant Colonel Jonathan Conricus, an army spokesman, adding that troops were scanning the area.

No casualties were reported on the Israeli side of the lines, where special forces had been lying in wait, aided by observation teams and permanent cameras, after the military noticed irregular activity at night during the past week, Lt Col Conricus said.

Israeli forces have been on elevated alert in the north in recent weeks, and particularly over the past week, after Israel said it had thwarted a raid by a Hezbollah "terrorist squad" armed with assault rifles in a disputed area along its northern border with Lebanon.

The latest event took place near Tel Fares, in the southern Golan Heights, in the same spot at which Israel had operated a field hospital to provide medical care for Syrian civilians during the Syrian civil war under the so-called Operation Good Neighbour, which is now defunct.

The location is within Israeli-controlled territory, just across from a reinforced steel security fence but west of the old, internationally recognised cease-fire line that forms Israel's boundary with Syria.

The military issued a 32-second, grainy, edited video showing four silhouetted figures approaching the fence then being struck down by fire as they retreated at an amble over the rough terrain.

Lt Col Conricus said that the target of the improvised explosive devices that the militants had planted would probably have been Israeli soldiers who occasionally patrol the area, where there is an Israeli military post that is not permanently staffed.

Israel held Syria responsible for any hostile activity emanating from its territory, he said. Syria did not immediately comment on the Israeli reports.

No special restrictions were placed on Israeli civilians living in the Golan Heights or northern Israel, indicating that the military was not anticipating any immediate retaliation.

The events overnight came after what the Israeli military said was a thwarted raid by Hezbollah, the Lebanese militant organisation, last Monday.

Israel said it had repelled the squad with small arms, tank and artillery fire, and that the men had fled back into Lebanon, while firing back, but Hezbollah denied that account. Hezbollah said that weapons had only been fired from the Israeli side.

Israel had cast the raid as an expected, and failed, retaliation attempt from Hezbollah for the killing of one of its operatives in a strike in Syria about a week before that was attributed to Israel. Hezbollah said that retaliation for the killing in Syria was still coming.

The Israeli military did not release any video of the thwarted raid, raising questions about what exactly had happened.

Israeli analysts said that the military had deliberately refrained from killing the Hezbollah squad, because it did not want to inflame the situation, and that both sides were calibrating their actions with that in mind.

The military did not explain why the Hezbollah squad was allowed to escape but said its decisions stemmed from a range of strategic considerations.

The decision not to release video or evidence of findings on the ground from that episode may have been intended to avoid embarrassment on both sides: for Hezbollah, in the form of evidence of a failed operation; and for Israel, in the sight of the militants fleeing unharmed.

Prime Minister Benjamin Netanyahu of Israel and his defence minister Benny Gantz both warned at the time that Israel would act forcefully to prevent any entrenchment by Iran or its proxies along its northern borders and was prepared for any scenario.

Iran and Hezbollah became involved in Syria to support the government of President Bashar Assad in its battle against insurgents. Israel has accused Iran and its proxies of trying to establish forward bases against Israel across the lines in the Golan Heights and of transferring advanced weapons to Hezbollah in Lebanon.

Lt Col Conricus said early Monday that Israel could not confirm any link between the group hit in the latest attack with Hezbollah or with the Iranians, adding that many smaller jihadi factions were active in the area, on Syrian soil.

On July 24, Israel carried out airstrikes near its border with Syria on targets belonging to the Syrian army after munitions had been fired toward the Israeli-controlled part of the Golan Heights, according to the Israeli military. The Syrian military reported that two of its members had been wounded.