Smoke billows from the site of an explosion in central Baghdad, 19 June 2007

A truck bomb near a Shiite mosque in Baghdad has killed at least 78 people and wounded at least 218 others. Meanwhile, thousands of Iraqi and U.S. forces have launched an offensive against terrorist havens northeast of Baghdad, killing at least 22 militants. From northern Iraq, VOA's Margaret Besheer has more.

The explosion outside the Khillani mosque in central Baghdad rocked the busy Sinak commercial area, damaging buildings and burning cars. A thick plume of black smoke could be seen rising over the area, and gunshots could be heard following the blast.

Scores of Iraqis were killed and injured in the explosion, and officials said the death toll could rise.

A picture shows destroyed Shi'ite Imam Askariya shrine in the restive city of Samarra, north of Baghdad, 13 June 2007

The explosion occurred two days after officials lifted a vehicle curfew imposed after last week's attack on the Shi'ite Askariya shrine in Samarra. No one was killed in that attack, but the shrine's twin minarets were destroyed.

An attack on the same shrine 16 months ago damaged its famed golden dome and set off the current cycle of sectarian warfare that has killed thousands of Iraqis and displaced millions more.

Meanwhile, northeast of Baghdad, in Baquba, the capital of restive Diyala Province, about 10,000 U.S. and Iraqi troops backed by jets and helicopters carried out operations against suspected al-Qaida militants.

Authorities imposed a curfew in Baquba as intense fighting broke out, with police fanning out across the city and using loudspeakers to warn people to stay indoors.

Military officials say many fighters have fled the Baghdad area since the new security plan was launched in February. The current operation is aimed at clearing out al-Qaida safe havens in Diyala province, which has seen a surge in violence in recent months.

Iraqi National Security Advisor Mouaffac al-Rubaie asked the Iraqi people to remember that their country has one enemy and it is al-Qaida and its supporters. He said all Iraqis must work together and cooperate to face them.

He said this will be a decisive round in destroying al-Qaida and breaking its back in Iraq. He promised that in the coming weeks, Iraqis would see many big operations and victories.