Baghdad ? Four U.S. soldiers were killed by roadside bombs Tuesday, the deadliest day for American forces in Iraq since combat troops pulled back from urban areas more than two months ago.

The separate attacks in Baghdad and in northern Iraq showed the dangers still facing U.S. troops as they drastically scale back their presence and prepare for a full withdrawal by the end of 2011.

The monthly U.S. death toll has declined sharply this year, falling into single digits for the first time, with American troops shifting to a mainly support and training role in line with a security pact that took effect on Jan. 1. August saw the lowest monthly toll since the war began in 2003, with seven U.S. deaths.

But attacks have persisted since American troops withdrew from population centers on June 30 — as required under the security deal — and Iraqi forces have borne the brunt. Bombings and shootings killed at least 10 Iraqis on Tuesday. The attacks have heightened concerns about Iraqi forces’ ability to protect the people and raised fears of resurgent violence ahead of January’s parliamentary elections.