Twin car bombs killed 19 people in the Shiite holy city of Karbala in southern Iraq on Monday, while four people died in a suicide attack on a Saudi-funded television channel in Baghdad.
The blasts in Karbala, where commemoration ceremonies are due to begin on Wednesday, occurred at around 7:00 pm (1600 GMT) and left at least 47 wounded, interior ministry and medical officials said.
One of the explosions struck on the southern outskirts of the city, which is the site of revered shrines to Imam Hussein and Imam Abbas, but it was unclear where the second bomb detonated.
The car bombs exploded two days before the birthday of Mahdi, the 12th and the last imam. Shiites, who make up the majority of Iraq's population, believe the missing imam will return to Earth on the Day of Judgement.
Hundreds of thousands of pilgrims are expected to descend on Karbala and the nearby holy city of Najaf for the ceremonies.
Meanwhile, a suspected Al-Qaeda suicide bomber blew up a car in front of the Baghdad offices of Al-Arabiya television, killing four people, a month after the Dubai-based channel was warned of insurgent threats.
The bomber struck at around 9:30 am (0630 GMT) before the station's bureau in the city centre, leaving a massive crater and sending a plume of smoke into the air that could be seen from several kilometres (miles) away.
Majid Hamid, a journalist for the pan-Arab satellite channel, said four people were killed -- three security guards and a female office assistant. That toll was confirmed by an official at Al-Yarmuk hospital in west Baghdad.
An interior ministry official, speaking on condition of anonymity, put the casualty toll at three dead and 16 wounded. Former deputy prime minister Salam al-Zawbayi was among the wounded.
"There was a huge explosion that shook the building -- all the rooms were damaged," Al-Arabiya journalist Tareq Maher told the channel in a live broadcast.
The street in front of the channel's offices was covered in shards of glass and debris, and nearby buildings showed signs of damage as did several cars.
Baghdad security spokesman Major General Qassim Atta accused Al-Qaeda of being behind the attack.
"These are the methods of Al-Qaeda," he told AFP. "The goal of this operation was to attract media attention."
Atta said the explosives-laden vehicle had passed through a checkpoint, and charged that there may have been "cooperation" between the car's driver and the guards.
Major General Jihad al-Jaabari, the head of the Iraqi army's explosives handling unit, said the bomber was an Iraqi and added that the vehicle was carrying more than 100 kilogrammes (220 pounds) of ammonium nitrate.
"He was waved through, but if they had searched him, it would have been easy to find the explosive material," Jaabari said.
Monday's bombing was the latest sign of the threat facing journalists working in Iraq, and came just a month after Al-Arabiya closed its Baghdad offices citing government warnings of a threat of insurgent attack.
A total of 141 journalists and media workers, the vast majority of them Iraqi, have been killed since the US-led invasion of 2003, according to the Committee to Protect Journalists (CPJ).
Al-Arabiya, which is perceived by extremist groups as pro-Western, has been no stranger to attack by suspected Sunni Arab insurgents or pressure from Iraq's Shiite-led government.
In October 2006, a car bomb targeting the channel's then bureau killed seven people and wounded 20.
And in February 2006, presenter Atwar Bahjat and two colleagues were kidnapped and murdered in the mainly Sunni town of Samarra as they covered the bombing of a revered Shiite shrine, an attack that plunged Iraq into sectarian bloodshed.
The channel's ownership by Saudi and other Gulf investors has also made it the focus of suspicions by Iraq's government that its news agenda reflects the concerns of their Sunni governments.