The Lebanese army claims there is a “plot” to drag Lebanon into the Syrian war. The ‘plot’ – ‘al-moamarer’ – is a feature of all Arab states. Plots come two-a-penny in the Middle East. What the military authorities really fear is that Sunni Muslim Salafist groups – perhaps paid by the same Gulf backers as the Sunni rebels fighting the Assad regime – have embedded themselves in the Lebanese population. The army suspects they exist deep in the northern Bekaa valley around the village of Arsal and in the northern city of Tripoli, as well as in Beirut and Sidon.

What the Lebanese army is not saying on the record – but which it acknowledges privately – is that large numbers of “Syrian” rebels are in fact Lebanese. They are being brought home to Lebanon to be buried, as are the hundreds of Shia Hezbollah fighters dying alongside Syrian troops in the battle for Qusayr and – soon, perhaps – for the great city of Aleppo.

In the ancient Roman-Crusader city of Tripoli yesterday, Lebanese soldiers were still tearing down sandbag barricades set up along dozens of streets by unidentified Sunni gangs in the dirt-poor Bab el-Tabaneh district, in the desperate hope that they can reclaim the suburb for the central government and prevent these districts turning into Salafist fiefdoms.

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When I visited this same district two weeks ago – it was under constant sniper fire from the Alawite-Shia hilltop of Jabal Mohsen, which largely supports the Assad regime – I met several fighters who would not identify themselves with any major militia, of which there are now at least 25 in Sunni areas of Tripoli. One of the largest is a Salafist group led by a man called “Osam” Sabbagh who, officially, at least, does not wish to participate in the fighting.

“Not all the Salafists are al-Qa’ida people,” a gunman who would call himself only Khaled insisted. “But the Salafists come and talk to us and we have no problem with them.” Many in the same Sunni slum streets – where giant bedsheets are strung across alleyways just as they are in Aleppo to prevent sharp-shooters from killing them – say they will not let the Salafists take over their district. Yet unless the army’s latest operation, authorised by the army command in Beirut and supported by the former Christian general Michel Sulieman – who is now the President – is successful, Khaled and his comrades may be powerless.

Privately, the army has learnt a lot about the “silent” creation of Salafist groups. A few Lebanese journalists have tried to convey these details – but largely on the inside pages of their newspapers. A Sunni anti-Assad rebel fighter from Baalbek, Hussein Dergham, for example, was killed in defence of Qusayr and has been brought home for burial. Three other Lebanese Sunni men from Baalbek were killed in a suburb of Qusayr but their remains have still not been recovered – and may never be, now that the town has fallen to Syrian troops and Hezbollah.

For the army, these dead men represent other ghosts. Many Lebanese have now forgotten how Islamists, from both Lebanon and other Arab countries, took over the Palestinian refugee camp of Nahr al-Bared north of Tripoli in 2007. Ironically, these gunmen of Fatah al-Islam were sent into Lebanon from what was then the super-stable Assad regime in Damascus. After a 105-day siege, Lebanese troops captured 215 of the Islamists – some are today still on trial in Beirut, others have fled to Sidon – but at a cost of 168 of their own soldiers’ lives and 226 Islamist dead. Up to 500 soldiers were wounded. In one Sunni village in the hills above Tripoli, residents refused to allow one of the Islamist dead to be buried because their own Sunni sons were among the army’s “martyrs”.

Now the cemetery “tables” are being ghoulishly turned. When a Hezbollah fighter called Saleh Sabbagh – a Sunni who converted to Shiism – was returned to a Sidon Sunni cemetery for burial last month, supporters of a local anti-Assad Sunni sheikh blocked the graveyard entrance with sandbags and burning tires, one of them screaming that the man’s corpse should be thrown into the sea. Sabbagh, who was killed fighting anti-Assad rebels in Syria, was subsequently interred in a Shia cemetery, but stones were thrown between rival groups and gunfire broke out later in the evening.

In the northern Lebanese border village of Wadi Khaled, members of the anti-Assad Jabhat al-Nusra rebels, which the army suspects may have strong links with the original Fatah al-Islam, began chanting outside the village mosque. And other supporters of Jabhat al-Nusra are reported to have emerged on the streets with banners near the Cite Sportive in Beirut, close to the airport highway – the first appearance of the rebel Islamist group in the Lebanese capital.

The Lebanese army and internal security have amassed other details – infinitely more chilling – about the Islamist groups. One man, identified only as Adnan, told the Lebanese military how Sunni imams were issuing “fatwas” urging them to assault opposition families inside Syria. Adnan, according to the military, said that his group had executed 13 Syrian government troops – three of them by beheading – and admitted that he had entered a Turkman village on the outskirts of Qusayr, shot a man in the legs and then raped his daughters, aged seven, eight and 10. He then – according to a report buried deep inside a long article in one Beirut newspaper – shot all four dead.

To the great consternation of the Lebanese army, up to 20,000 Syrian Sunni refugees from Qusayr have just poured into the Arsal, where three Lebanese soldiers on watch for anti-Assad weapons smugglers were murdered last week. The influx of refugees now equals the town’s total population. Little wonder that the Beirut government is now talking of preventing future flights of Syrian refugees into the country.

From their ultra-safe environment outside Lebanon, Gulf leaders are now encouraging the fury of the country’s Sunnis. The grand mufti of Saudi Arabia – America’s bosom friend in the Gulf – supported the televangelist preacher Youssef al-Qaradawi in calling for all young Sunnis to fight the Assad regime – and Hezbollah – inside Syria. It is easy to dismiss this incendiary demand as part of the great Sunni-Shia divide, one which America, in its support for the Gulf Sunni states and its hatred of Iran and Hezbollah, is happily stoking.

And Hezbollah has done itself no favours in joining Assad’s forces in Qusayr. Lebanese Sunnis have been asking themselves whether Hezbollah – for years the much-touted “resistance” to Israeli occupation in Palestine – had been under the mistaken impression that Qusayr was a suburb of Jerusalem. On Sunday, Islamists with guns and sticks attacked both unarmed male and female anti-Assad protestors outside the Iranian embassy in Beirut, killing the head of the movement’s student organisation, Hashem Salman. One Lebanese newspaper’s front page headline yesterday read: “Who from the Hezbollah or the Iranian Guards murdered Hashem Salman?”

A few hours later, 10,000 Sunni supporters of the Free Syrian Army gathered in Sidon. I counted 750 hitherto-unseen black-uniformed militia guards. They carried radios but no guns. Alas, it is not the same elsewhere. Only seven days ago, there were assassination attempts against two pro-Hezbollah Sunni sheikhs. One of them, whose car was sprayed with bullets in Sidon, had recently condemned Hezbollah’s intervention in Qusayr. But for some, there are no politics in death. In Tripoli two days later, a harmless beggar called Ahmad Soboh sat down on his usual pavement spot near a café where he was usually given food and water. A sniper shot him dead. Perhaps he was so miserable, some locals suggested, that he wanted to take his own life.