BAGHDAD - A suicide bombing Wednesday in the city of Baqouba killed seven people and wounded 22, police said, while authorities increased the death toll from a Baghdad suicide attack at a funeral the previous day to 36.

The bombings were a reminder of the dangers that persist despite the recent decline in violence in Iraq — and of the peril for mass gatherings in a country where the bereaved often find themselves targets.

In Wednesday's attack, the bomber detonated his explosives near a hospital in the center of the city, the capital of volatile Diyala province, 35 miles northeast of Baghdad, said police Col. Raghib al-Omari.

The dead included a policeman and two members of a U.S.-backed armed volunteer group, the Brigades of 1920s Revolution, a police officer said.

The volunteer groups — predominantly Sunni tribal groups known as Awakening Councils who have turned against al-Qaida and are paid by the U.S. military to protect their areas — have been credited with contributing to an overall decline in violence by 60 percent since June.

But the rapidly expanding movement, singled out by Osama bin Laden in a recently released audio message as a "disgrace and shame," is increasingly becoming a target. On Monday, a suicide bomber targeting Awakening Council members killed 12 people in Tarmiyah, north of Baghdad.

In the capital, relatives wept outside a hospital as the remains of victims from Tuesday's bombing — the deadliest in Baghdad since August — were placed into coffins. Police increased the death toll by four to 36, and said 37 people had been wounded.

The attacker detonated his explosives amid men gathered in Baghdad's eastern Zayouna neighborhood for the funeral of Nabil Hussein Jassim, a retired Iraqi army officer who was one of 14 people killed last week in a car bombing blamed on al-Qaida in Iraq.

"At the end of a three-day mourning period, a terrorist blew up himself in the mourning tent, leaving bodies scattered," one of the wounded men, who gave his name only as Abu Hasanain, told AP Television News from his bed in al-Kindi Teaching Hospital.

In the same neighborhood, a roadside bomb targeting a police patrol wounded six people Wednesday — three police and three civilians, a police officer said on condition of anonymity because he was not authorized to release information.

To the north in Mosul, 225 miles northwest of Baghdad, police said they detained a senior local al-Qaida fighter in a joint operation with police from nearby Tikrit.

The suspect, Adnan Khalil al-Faraj, is believed to be a senior al-Qaida military commander for Mosul and Tikrit, said Brig. Abdul Kareem al-Jubori of Nineveh province's police.

Despite continuing attacks, there has been a noticeable decrease in violence across the country, compared with late 2006 and early 2007, when many feared Iraq was heading toward civil war.

Separately, an adviser to Prime Minister Nouri al-Maliki said Wednesday that negotiations are expected to begin in mid-January between Iraq and Iran over the cleaning up the strategic Shatt el-Arab waterway.

Talks will focus on removing soil that has eroded into the Iraqi side of the waterway, dredging out sunken ships and removing land mines left over from the Iraq-Iran war in the 1980s, said Sami al-Askari.

No date has been set for the meeting, but it is expected to take place this month, al-Askari said. Talks will not involve renegotiating the border through the disputed waterway, which runs between Iran and Iraq and leads to the Persian Gulf.

The waterway provides Iraq with its only outlet to the sea, and tensions have flared sporadically between the two countries over its delineation.

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Associated Press writers Qassim Abdul-Zahra and Diaa Hadid contributed to this report.