Amman/Cilvegozu (Reuters) - Rebels seized control of sections of Syria's international borders and torched the main police headquarters in the heart of old Damascus, advancing relentlessly after the assassination of President Bashar al-Assad's closest lieutenants.

The battle for parts of the capital raged into the early hours of Friday, with corpses piled in the streets. In some neighborhoods, residents said there were signs the government's presence was diminishing.

Officials in neighboring Iraq confirmed that Syrian rebels were now in control of the Syrian side of the main Abu Kamal border checkpoint on the Euphrates River highway, one of the major trade routes across the Middle East.

Rebels also claimed control of at least two border crossings into Turkey at Bab al-Hawa and Jarablus, in what appeared to have been a coordinated campaign to seize Syria's frontiers.

In Damascus, a witness in the central old quarter district of Qanawat said the huge headquarters of the Damascus Province Police was black with smoke and abandoned after being torched and looted in a rebel attack.