The move comes amid claims by a Palestinian faction leader that his men are holding six Lebanese soldiers captive and a report by the UN envoy calling for action to disarm the fighters.
Officers said about 500 soldiers backed by 50 armoured cars were now deployed around the camps in the foothills of the Anti-Lebanon range that marks the border, two operated by the Popular Front for the Liberation of Palestine-General Command (PFLP-GC) and five by Fatah-Intifada.
Soldiers on Thursday were seen manning checkpoints on all access roads to the bases and operating armoured patrols on the tracks linking PFLP-GC bases in Sultan Yacub and Kfarazabad to those of Fatah-Intifada around Halwa, 15km away.
"We have cut off all the Palestinian bases' supply routes and the land links between them," one Lebanese officer said, asking not be identified.
"We have also deployed troops on eight dirt tracks used by the Palestinians to bring in men and materiel from Syria."
The immediate trigger for Wednesday's deployment around the bases was the murder of a surveyor working for the Lebanese military the previous day, which commanders blame on fighters from Fatah-Intifada.
In a new twist to the stand-off, PFLP-GC leader Ahmad Jibril said in comments published on Thursday that his men were holding six soldiers captive.
"We detained six Lebanese soldiers, one of them an officer, after they approached one of our positions in Kfarazabad on Wednesday," Jibril was quoted as saying in an interview with the Beirut daily An-Nahar.
"We notified the Lebanese army ... and maybe we will be able to settle the issue in the evening [Thursday]."
"We detained six Lebanese soldiers, one of them an officer, after they approached one of our positions in Kfarazabad on Wednesday"
A military source in Beirut denied that any soldiers had been captured and said the high command would be putting out a statement. But the communique was later cancelled.
Jibril also charged that the army had detained three PFLP-GC fighters, one of them a commander, but he gave no details about the circumstances of their capture.
The siege of the Palestinian bases came as UN envoy Terje Roed-Larsen presented a report in New York charging that the continued presence of armed Palestinian fighters in Lebanon violated a Security Council resolution adopted in September last year.
That text called for the withdrawal of all foreign troops, eventually prompting Syria to end a 29-year military presence in April, as well as the disarmament of all militia groups, Lebanese or Palestinian.
In a separate development, French President Jacques Chirac urged Syria on Thursday to cooperate with the investigation into the killing of former Lebanese prime minister Rafiq al-Hariri.
He hinted Syria could face international sanctions if it fails to do so.
"Syria must cooperate," Chirac said after a day-long meeting of European Union leaders at Hampton Court, England. "Very evidently it has not cooperated. We have to make [sure] it is made to cooperate."
Chirac added he was also "personally in favour of the creation of an international tribunal" to prosecute those guilty of al-Hariri's killing.
The French president said Mehlis'
mandate may require extension
Chirac said Mehlis' mandate "may require further extension".
"We have to give the means to Mr Mehlis to continue his inquiry and to draw all the necessary conclusions," he said. "We have to have some system where justice is done."
Syria on Thursday criticised the UN resolution, saying it was part of a US attempt to blacklist Damascus the same way it did with Iraq before invading the country.
Damascus has sharply criticised the UN report, but expressed willingness to cooperate in the continuing investigation.