Another major Iraqi city is on fire, with scores of civilians killed and hundreds injured in some of the worst fighting since the 2003 American invasion.

Pitched fighting in the southern city of Diwaniya between armed supporters of radical Shiite Cleric Moqtada al-Sadr and American and Iraqi forces has been dragging on since Sunday [Aug. 27].

Diwaniya, home to nearly 500,000 people, is capital of al-Qadisiya Province. Sadr is believed to command a large following in the city, which is seen as a major Sadr stronghold. Until recently, the city had been relatively quiet.

Sadr's fighters are entrenched in residential areas of the city, and bids to dislodge them are bound to result in terrible suffering for the population.

On Tuesday [Aug. 26], Sadr's group was said to have reached a ceasefire agreement with U.S. and Iraqi troops, but sources in Diwaniya described the deal as "fragile."

The fighting erupted when foreign troops arrested a Sadr militia leader.

It is unclear why the Shiite-dominated government [the government in Baghdad] has decided to move against Sadr, as he has active deputies in Parliament who make up part of the ruling Shiite collation.

An Iraqi army captain, who wished to remain anonymous for security reasons, said Sadr's militiamen were pouring into the city from villages and towns across the province. He also said that as a show of force, the government is sending "more reinforcements" to the city.

"If fighting erupts again, and this is what is expected, we'll have a very bad situation," he said.

The Iraqi authorities accuse the Sadr militia of sabotage, assassination and kidnapping. But a Sadr representative in Diwaniya, Saheb al-Ameri, denied his group's involvement in such acts.

"The Mahdi Army [Sadr's militia] has nothing to do with these things (violence). There are other groups who do such things and then point the finger at us," said Ameri.

Iraqi troops assisted by U.S. Marines have imposed a curfew on the city, and many families are reported to have fled their homes for safer areas. Shops have been closed since Sunday [Aug. 27], and the city has been without electricity and water for four days.