Nusra Front, an al-Qaeda-affiliate that is among the armed Sunni groups engaged in Syria's conflict, has threatened to kill two more Lebanese soldiers unless the wives of some of its commanders are released from detention.

The threat comes a day after the group killed a young Lebanese police officer it was holding captive.

In a statement to local media on Sunday, Nohad Machnouk, Lebanese interior minister, said publicising the arrests of the female detainees was a mistake.

He said their arrests "will draw the attention of international organisations and religious figures to us, especially since we do have proof that the detainees were planning an operation.

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"Their contact with terrorists is not something that a case can be built on".

Lebanon is experiencing a spillover of the nearly four years of violence that has gripped neighbouring Syria.

Lebanese fighters opened fire on and burned Syrian refugee tents in north Lebanon, wounding two refugees, security sources said on Sunday.

And on Saturday, fighters and protesters took to the streets after Nusra Front said it killed a captured a Lebanese policeman it named as Ali al-Bazzal, to avenge the arrest of family members of its commanders.

Relatives of another 25 troops and policemen being held hostage cut off several roads in Beirut and elsewhere in Lebanon, demanding the government work for their immediate release.

Bazzal was the fourth hostage reportedly killed by their captors from the 30 troops and policemen kidnapped in August, after a major battle in Arsal in eastern Lebanon on the border with Syria.

A fifth soldier died from wounds he suffered during the Arsal battle four days into the hostage crisis.

None of the dead troops' bodies has been handed over to Lebanese authorities, said the government source.

Source: Al Jazeera and agencies