Thursday's bombings come one day after 53 people were killed, including 32 at a Shiite funeral east of Baqouba.
The suicide blast near the Imam Hussein shrine in central Karbala, 80 kilometers (50 miles) south of Baghdad, killed 49 people and injured 52, Karbala police Col. Razaq al-Taie.
Pools of blood lay at the blast site, and television images showed men ferrying the wounded in pushcarts. The bomber appeared to have set off the explosion only about 30 meters (30 yards) from the shrine in a busy pedestrian area surrounded by shops.
A suicide bomber blew himself up outside a police recruiting center in the restive city of Ramadi, killing at least 30 people and injuring another 40, police and hospital officials said.
The attack happened at a police screening center in Ramadi, an insurgent stronghold 70 miles west of Baghdad. At least 30 people were killed, said Mohammed al-Ani, a doctor at Ramadi General Hospital and police Capt. Nassir al-Alousi.
The U.S. military did not have a casualty figure, but said that a suicide bomb exploded at 10:55 a.m. near the Ramadi Glass and Ceramics Works "where screening for Iraqi Police Officers was taking place."
Karbala has been relatively free of violence since December 2004, when seven people were killed and 31 wounded in an attack. In March of that year coordinated attacks from suicide bombers and preset explosions on Karbala's holy sites killed more than 100.
Wednesday, a suicide bomber killed 32 mourners and wounded dozens at a funeral for the nephew of a Shiite politician, one of several attacks across Iraq that killed a total of 53 people — making it the deadliest day since the Dec. 15 elections.
The increased violence came as Iraq's three major political parties were close to forming a coalition government that would include Shiites, Sunni Arabs and Kurds, according to a Shiite politician.
Iraq's election commission said it planned to release the results of its investigation into almost 2,000 complaints stemming from last month's parliamentary elections within the next two days.
In other developments:
More than 100 mourners were standing in a cemetery in Muqdadiyah, about 60 miles north of Baghdad, for the burial of a nephew of Ahmed al-Bakka when the bomber struck, the Diyala provincial police said. The cemetery was strewn with body parts and the tombstones were stained with blood.
At least 32 people were killed and 42 wounded, said Dr. Firas al-Nida of the Muqdadiyah hospital.
Al-Bakka had survived an assassination attempt Tuesday that killed his nephew. Al-Bakka is the head of the local Dawa party, led by Prime Minister Ibrahim al-Jaafari and a main partner in the country's largest Shiite political coalition, the United Iraqi Alliance.
Shiites have been targeted by extremist Sunni groups such as al Qaeda in Iraq, led by Jordanian-born terrorist mastermind Abu Musab al-Zarqawi.
A partner in the largest Sunni Arab political party denounced the attack at the funeral.
"The Islamic Party condemns such ugly acts that are aimed at dividing the country," said Nassir al-Ani. "The perpetrators want to cause divisions and hinder the political process in Iraq, but they will fail and we will establish a national unity government."
Insurgents attacked a convoy of 60 tanker trucks with rocket-propelled grenades and machine guns, destroying three of the tankers and damaging 15 others, said police Lt. Abdul Zahra Qassim. Three Iraqi army vehicles, which had been guarding the convoy, were also destroyed in the attack about 25 miles north of Baghdad, police said.
Tanker truck drivers had stopped transporting gasoline from Iraq's largest refinery in Beiji on Dec. 18 because of security concerns. The drivers began carrying fuel again this week after being promised increased security.
Roadblocks went up across Baghdad as police searched for the sister of Interior Minister Bayan Jabr, who was kidnapped Tuesday. Gunmen killed one of her bodyguards and seriously wounded another in the abduction.
A description of the suspects' car had been distributed to all checkpoints, said Lt. Thair Mahmoud.
Jabr is a member of the Supreme Council of the Islamic Revolution in Iraq, the country's largest Shiite party, and was formerly a senior official of the Badr Brigade, a militia that belongs to SCIRI. He has recently been the focus of criticism over allegations of torture and abuse of prisoners at Interior Ministry jails. Many of the those abused were Sunnis, the group thought to fuel the insurgency.
The three tickets — the Shiite United Iraqi Alliance, the Sunni Arab Iraqi Accordance Front and the Kurdish coalition — were working on a coalition government, an Alliance official said Wednesday, and were discussing a nominee for prime minister.
"We can say that the (three parties) are close to forming a new government," said Ridha Jawad Taqi, a member of SCIRI, which is coalition partner in the United Iraqi Alliance. "Meetings between the tickets will be resumed after announcing the final results of the elections."
An international monitoring team this week began to review results from last month's elections, including some of the hundreds of complaints filed. A member of Iraq's election commission said final results won't be announced until the international review was completed, meaning results might be delayed until mid-January.
Meanwhile, Adel al-Lami, general director of the Independent Electoral Commission of Iraq, said officials had almost finished working through all the complaints and would announce its findings within the next two days. The international team met with the IECI Wednesday to review the commission's procedures in dealing with the complaints, he said.
The separate international team agreed to review Iraq's elections after protests by Sunni Arab and secular Shiite groups that the polls were tainted with fraud.
Preliminary results give the governing United Iraqi Alliance a big lead, but one that would still require forming a coalition with other groups.