BAGHDAD — A series of bombings shook Baghdad for the third straight day Wednesday, killing 17 people and wounding more than 70, police said. The attacks were part of an upswing of violence in the capital this month that has set back recent security gains.

In the face of heightened violence in Baghdad, the Iraqi military said it was taking measures to curb "the increasing number of terrorist attacks" in the city. Military spokesman Maj. Gen. Qassim al-Moussawi said the measures would include stepped up intelligence gathering and pre-emptive strikes on suspected extremists.

The first car bomb ripped through a bustling shopping neighborhood in downtown Baghdad during the morning rush hour, killing four people and injuring 15.

A second car bomb exploded near a school in the Shiite-dominated Shaab neighborhood in north Baghdad. Iraqi police said five people were killed, and 12 wounded.

In the Shiite district of New Baghdad, a bomb exploded later and moments after, a parked car bomb blew up in the same area after police arrived on the scene of the first blast. It was not immediately clear how many were killed in each explosion, but police and hospital officials gave an initial toll of eight dead and 45 wounded.

The latest attacks follow two days of morning rush hour blasts in Baghdad that killed more than 30 people and wounded some 70.

Violence had fallen sharply in the capital before this month. But in the first nine days of November, there were at least 19 bombings in Baghdad, compared with 28 for all of October and 22 in September, according to an Associated Press tally.

Many of the attacks have targeted Iraqi police and army patrols, as well as government officials heading to work and commuters.

The rise in violence comes as U.S. and Iraqi officials try to hammer out a final agreement on a security deal that would keep U.S. troops in Iraq until the end of 2011. The security pact has drawn sharp criticism, especially from within the majority Shiite community.

The current U.N. mandate authorizing the U.S. presence in Iraq expires at the end of December. Without a security agreement or a new U.N. mandate, the U.S. military would have to cease operations in Iraq.

In an attempt to derail the pact, 10 Iraqi insurgent groups have agreed to ramp up attacks against U.S. and Iraqi forces, according to the SITE Intelligence Group, which monitors extremists.

But it is not clear who is responsible for the recent attacks in Baghdad.

In the volatile northern city of Mosul, unidentified gunmen killed two sisters from a Christian family as they were waiting in front of their house for a ride to work, police said. The women's mother was injured in the attack.

The attack in Mosul — an ethnically mixed city of Kurds, Christians and Arabs — comes after about 13,000 Christians fled the city last month in the face of threats and attacks from extremists. Some families have started returning to the city, although tensions linger.

Mosul has seen a spike in violence in recent months as the ethnic groups vie for power, and U.S. troops and Iraqi security forces continue to wage an intense battle with insurgents in the city.