Syrian rebels on defensive

BEIRUT The Syrian military opened a second urban front Friday, attacking the rebel stronghold of Homs with the most intense artillery barrage in months and putting opposition fighters there and in Syria’s largest city, Aleppo, increasingly on the defensive.

Syria’s civil war has been locked in a bloody stalemate, and embattled President Bashar Assad could extend his hold on power if he retakes Aleppo and Homs.

Amateur video from Homs, a symbol of resistance, showed black columns of smoke rising from the city, as loud explosions went off every few seconds.

While Assad stepped up attacks at home, tensions with neighbouring Turkey flared again Friday, reviving fears that the 18-month-old conflict in Syria could ignite a regional conflagration.

The crisis began on Wednesday, when a Syrian shell killed five civilians in a Turkish border town and triggered unprecedented artillery strikes by Turkey, coupled with warnings that Turkey would no longer tolerate such acts.

On Friday, a Syrian mortar round again hit inside Turkey, causing no injuries, and Turkish troops returned fire, the state-run news agency Anadolu said.

In the past, Turkey did not respond to stray Syrian shells, but Turkish Prime Minister Recep Tayyip Erdogan suggested Friday that those days are over. “I once again call on Assad’s regime and its supporters: Do not try to test Turkey’s patience, do not try to test Turkey’s limits,” Erdogan said.

Earlier in the day, Turkey had deployed more troops on its border with Syria.

The U.S sided with Turkey, condemning what White House spokesman Josh Earnest called the “aggressive actions of the Syrians.”