– Fierce clashes continued for a second day Monday between the army and gunmen loyal to a radical Sunni cleric in this southern Lebanese city, in an outburst of civil violence that reflected how deeply the war in neighboring Syria has undermined security in Lebanon.

At least 15 soldiers have died in the clashes, according to Lebanon’s official National News Agency. Reports varied on the death toll among followers of the cleric, Sheik Ahmad al-Assir, who was said to be hiding in his mosque with hundreds of his followers on Monday.

The news agency said at least two of his followers had been killed, and other local news outlets said as many as 30 had died. The sound of heavy weapons had ebbed downtown by Monday afternoon, but intermittent gunfire could still be heard. A Lebanese officer said the army had surrounded and entered Assir’s mosque, in the city’s Abra district.

The fighting represented some of the worst violence in Lebanon since the Syrian uprising began more than two years ago, fueling fears of the Syrian civil war’s contagion. More worryingly for many people here, the scenes in Sidon — of Lebanese battling each other in the streets — recalled 1975, and the start of Lebanon’s own 15-year civil war.

While Assir’s following was seen as marginal in Lebanon, some Sunnis, sympathetic to Syria’s rebel movement and frustrated with the lack of leadership from the mainstream Sunni Future movement, say Assir has provided an outlet for anger over Hezbollah’s role in Syria.