BAGHDAD (AP) — A bomb left on a Baghdad minibus and a suicide truck bomb north of the Iraqi capital killed at least seven people and wounded 34 others on Tuesday, officials said. The attacks followed a particularly bloody day that left more than 70 people dead.

The incidents are the latest in a spike of killings that has claimed more than 450 lives since the start of May, raising fears that Iraq is slipping back toward widespread sectarian bloodshed.

Five commuters were killed when a bomb exploded inside the bus while traveling through Sadr City, a Shiite-majority district in the city’s east, a police officer said. Five policemen and 20 civilians were wounded in that attack, he added.

Another police office said a suicide bomber set off his explosives-laden truck after passing a police checkpoint in the town of Tarmiyah to the north of Baghdad, killing a policeman and a civilian. Nine were wounded. The town is 50 kilometers (30 miles) north of Baghdad.

Two medical officials confirmed the casualties. All spoke on condition of anonymity as they were not authorized to release information.

On Monday, more than a dozen car bombs hit commercial areas in mostly Shiite areas of the Iraqi capital, killing 71 people and wounding nearly 200 others.

Alarmed by the recent bloodshed, UN envoy Martin Kobler pressed Iraqi leaders on Tuesday to do more to halt the violence, saying it is "their responsibility to stop the bloodshed now."

Kobler has repeatedly urged Iraqi officials to engage in dialogue as violence and political tensions have grown in recent weeks.

He warned political leaders Tuesday not to let terrorists benefit from their political differences, and predicted that "the country will slide into a dangerous unknown if they do not take immediate action."

No one has claimed responsibility for the recent wave of attacks, but such systematic bombings bear the hallmarks of Sunni insurgents under the leadership of the al-Qaida branch in Iraq, known as the Islamic State of Iraq. They appear aimed at drawing the country’s majority Shiites into an exchange of attacks like that which brought the country to the brink of civil war in 2006-2007.

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Associated Press writer Adam Schreck contributed to this report.