Fighting Continues in Aleppo and Homs

Both government forces and rebels reporting progress

(CNN) -- Clashes were reported Friday in Aleppo and Homs, two centers of opposition to Syrian government forces.

Here are the latest key developments in the nearly 18-month crisis:

On the ground: Shelling, violence continue

In Aleppo, the scene of fierce fighting in recent weeks, rebel fighters are clashing with government forces in the Saif al-Dawla, Hanano and Sakhour neighborhoods, the opposition Syrian Observatory for Human Rights said.

Regime forces are shelling several neighborhoods, it said.