BEIRUT, Lebanon — The Syrian Army on Monday deployed tanks and thousands of soldiers into the restive southern city of Dara’a and carried out arrests in poor towns on the outskirts of the capital, Damascus, in a sharp escalation of the widening crackdown on Syria’s five-week-old uprising, according to human rights activists and accounts posted on social networking sites. They said at least 25 people were killed in Dara’a, with bodies strewn in the streets.