Activists say Syrian government forces have killed at least 12 people in heavy shelling of a rebel-held district in the flashpoint city of Homs.

Activists say at least one child was among the victims in the artillery barrage Tuesday on the neighborhood of Baba Amro.

The casualty figures could not be independently verified because Syria restricts operations of foreign media.

The attack comes a day after Syria's army deployed tanks and other reinforcements around Homs in preparation for a possible ground assault.

Syrian forces have bombarded Homs for more than two weeks. The central city has been a major hub of the 11-month uprising against the autocratic rule of Syrian President Bashar al-Assad.

Activists also say security forces opened fire on demonstrators overnight in the capital, Damascus.

On Monday, the International Committee of the Red Cross said it is trying to broker a humanitarian cease-fire around Homs.

ICRC spokeswoman Carla Haddad said her agency has been in talks with Syrian authorities and rebels about ways of stopping hostilities to allow the delivery of humanitarian aid to affected areas.

Also Monday, U.S. Secretary of State Hillary Clinton said nations opposed to Mr. Assad's crackdown on the uprising will demonstrate his increasing isolation at a Friends of Syria meeting in Tunisia later this week.

Earlier this month, Russia and China vetoed a Western- and Arab-backed effort to pass a United Nations Security Council resolution endorsing an Arab League plan for Mr. Assad to cede power. But Arab League Secretary-General Nabil Elaraby said Monday he believes Russia and China may be shifting their positions on the Syrian crisis.

Human rights activists say the violence has killed at least 6,000 people.

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