Gunmen have ambushed a bus in the Iraqi capital, Baghdad, killing at least six people, police said.
One bomb was quickly followed by a second explosion
The attack happened in the Amariya district in the west of Baghdad - a mainly Sunni area.
Earlier on Monday, a series of explosions in Baghdad killed at least 10 people and injured more than 40.
Two of the bombs struck the run-down Shia area of Sadr City in what appear to be reprisals for the attacks on Sunnis on Sunday.
A third bomb exploded in central Baghdad on Monday but no casualty figures are yet available.
There has been an upsurge in sectarian violence in Iraq in recent months, raising fears of a civil war.
In the first attack, car bomb exploded at a car repair shop, police said. A second explosion came within minutes.
Trail of violence
Some reports said a suicide bomber drove into a crowd gathered near the site of the first explosion, others said a mortar attack caused the second blast.
In other incidents:
- Police found five unidentified bodies in Suwayra, 40 km (25 miles) south of Baghdad.
- At least three people were killed and seven wounded when a suicide bomber blew up a truck outside the offices of the Kurdish party of President Jalal Talabani in the northern city of Kirkuk, police said.
- A policeman was killed and four people were wounded by a roadside bomb near the city of Hilla, police said.
- A member of the provincial council in Diyala province, Adnan Iskandar al-Mahdawi, was killed in a drive-by shooting.
- A roadside bomb in the centre of Baghdad injured five policemen.
Our correspondent says Monday's blasts appear to be reprisals for Sunday's bloodshed when Shia gunmen roamed the Sunni neighbourhood of Jihad in the west of Baghdad, dragging Sunnis from their cars and shooting them.
Many were shot execution-style in the street.
Women and children were among the casualties of the Jihad attack
Police maintain that more than 40 died, disputing a claim by a senior government official, Haidar Majid, that only nine people were killed.
Hours after the shootings, a double car bomb attack near a Shia mosque in Baghdad's northern Kasra district killed about 20 people and wounded dozens of others.
Appeal for calm
On Monday a curfew was imposed in the Sunni neighbourhood of Dora for fear of further attacks.
Sectarian violence has plagued parts of Iraq for several months. There are many accounts of Shia families living in Sunni neighbourhoods receiving death threats and being forced from their homes, and of Sunnis being forced from Shia neighbourhoods.
Radical Shia cleric Moqtada Sadr appealed for calm following Sunday's shootings.
His Mehdi Army militia, which has a strong presence in Sadr City, was accused of involvement in the attacks, but his office denied any responsibility.
Presidential security adviser Wafiq al-Samaraie told al-Jazeera television that the country was "at the gates of civil war" unless "exceptional measures" were taken.
The wave of violence comes two weeks after Prime Minister Nouri Maliki launched a national reconciliation plan to end the bloodshed between Sunni and Shia in the country.