Syrian rebels and government forces fought fiercely in Damascus for a third straight day, according to Washington Post and other reports.

This image made from video provided by Shaam News Network on Tuesday purports to show a Syrian tank in Damascus, Syria. (Anonymous/AP)

The Post’s Liz Sly wrote: “Damascus has become a war zone. This is the historic Midan district today. Wow.”

Syrian government helicopters have also been shelling rebels in the capital. A video depicts local residents screaming as they witness earth-shaking blasts, burning homes and plumes of smoke after a group of helicopters flies overhead:

The Post reported, citing the Britain-based Syrian Observatory for Human Rights, that “rebel forces from elsewhere in Syria were converging on Damascus to help with the fight.” That development was adding to “the sense that some kind of final showdown may be at hand,” The Post’s report said.

“The question now remains if the Syrian government decides to isolate Damascus, how long can the resistance hold its breath,” said Cairo-based activist Rami Jarrah in an e-mail. “This really depends on the next few days and what can be organized on the ground efficiently.”

Midan was one of the hardest-hit areas, but Jarrah said on Twitter that the violence had touched multiple neighborhoods across Damascus:

Reports that #battalions from west #Damascus have situated in #Kafarsooseh today #Syria

— Alexander Page (@AlexanderPageSY) July 17, 2012

Ongoing heavy clashes in #Yarmouk of #Damascus 17 year old Ahmad Tinawi shot dead by sniper gunfire just a while ago #Syria

— Alexander Page (@AlexanderPageSY) July 17, 2012

Large arrest campaign now taking place in #birnea street just after a large demonstration kicked off outside salahiddeen mosque #Damascus

— Alexander Page (@AlexanderPageSY) July 17, 2012

One Syrian who is identified as tweeting from Damascus also provided video of smoke billowing out of the Nahr Aisha neighborhood:

Thick smoke rising from Nahr Aisha neighbourhood of #Damascus due to shelling… #Syria

— Sami al-Hamwi (@HamaEcho) July 17, 2012

A senior commander with the opposition Free Syrian Army said the strategy was to “bleed down” government forces in the stand-off.

Sami al-Hamwi posted a snapshot of a security bus allegedly destroyed by rebels:

FSA destroy a security forces bus in Midan neighbourhood of #Damascus #Syria…

— Sami al-Hamwi (@HamaEcho) July 17, 2012

Jarrah and others also tweeted that government forces had established a sort of base at a local hospital:

Confirmed: Mushtahid hospital has become a depot for government forces, the #babmusala square is packed with over 2000 government elements

— Alexander Page (@AlexanderPageSY) July 17, 2012

View Photo Gallery: Military defectors and civilians make up Syria’s main opposition army group.