At least 45 people have been killed and up to 150 wounded by a blast in the northern Iraqi city of Arbil, Kurdistan Health Minister Jamal Abdel Hamid told Aljazeera by phone.
Later on Wednesday, a car bomb killed nine members of the Iraqi National Guard and wounded 20 people in Baghdad's Doura district, police said.
Speaking about the Arbil attack, Abdel Hamid said "all the ministry's institutions and hospitals have been placed on alert to provide treatment to the wounded", adding that citizens rushed to hospitals to donate blood.
When asked whether the number of fatalities is likely to rise, he said: "It is natural that the number will increase given the large number of wounded, but we will try our utmost to reduce the figure."
A Sunni anti-US group, Ansar al-Sunnah, claimed responsibility for the attack, saying in a statement posted on the internet that it was in revenge for Kurdish cooperation with US forces. The same group took credit for a 2004 twin suicide bombing also targeting Kurds in Arbil that killed 109 people.
Earlier, the US military said an Iraqi carrying hidden explosives set them off inside a police recruitment centre in Arbil, killing at least 50 Iraqis.
The attack occurred as people were applying for Iraqi police jobs at the recruitment centre, according to US military spokesman Captain Mark Walter.
Police officer Shwan Muhammad said it was not immediately clear where the bomber had hidden the explosives under his clothing or in something he was carrying.
Other media reports gave higher casualty figures, with Reuters quoting health sources as saying at least 60 people were killed and as many as 150 wounded.
Arbil, 350km north of Baghdad, is the domain of Massoud Barzani's Kurdistan Democratic Party (KDP), one of the two Kurdish factions in Iraq.
Kurdish security forces inspect
the site of Wednesday's blast
In an interview to Aljazeera on Wednesday, Saru Qadir, the KDP's chief information officer, said: "A hush has descended on Arbil following Wednesday morning's terrorist attack. Public mood at present is one of intense sadness."
He continued: "Terrorism is threatening all Iraqi cities and areas. Kurdistan had enjoyed calm since the beginning of the changes in Iraq, with the Kurdish regional government in charge of security matters in addition to administrative and social affairs."
Qadir said because Kurdistan province is a very important part of the federal state, "it is facing threats from terrorist organisations and remnants of the toppled Baath Party".
He added: "The whole of Iraq is threatened by terrorists. The safest area is Kurdistan, which has always been a target for terrorists.
"Today terrorists exploited a security lapse, enabling one of them to blow himself
up among a crowd of police volunteers and
Kurdistan Democratic Party information officer
"Today they exploited a security lapse, enabling one of them to blow himself up in a crowd of police volunteers and inflict casualties."
Also on Wednesday, an Iraqi National Guard convoy came under a car-bomb attack on the main road in al-Wihda area, south of Baghdad, Aljazeera reported.
US soldiers killed
In Baya district, also located south of Baghdad, three Iraqis were injured after an explosive device hit a US military patrol.
The blast damaged a number of the cars. Some local residents were arrested from the site of the explosion.
Earlier, the US military said two US soldiers had died in separate roadside bomb attacks in Baghdad on Tuesday.
This was the second attack on
Kurds in the span of a week
Further information was withheld pending notification of the victims' relatives.
As of 5 May 2005, 1593 members of the US military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.
Iraqi security forces captured a son of one of ex-Iraqi president Saddam Hussein's half-brothers in a raid on a suspected hideout.
The Iraqi government said on Wednesday that the operation took place earlier this month near Tikrit, 130km north of Baghdad.
Several other suspects were arrested in the raid that netted authorities a cache of explosives, the government said in a statement.
Ayman al-Sabawi is the son of al-Sabawi Ibrahim al-Hassan, a half brother of Saddam, who served as a presidential adviser before the US-led invasion.
Al-Hassan was captured on 26 February.
Ayman al-Sabawi "played a particularly active role in sustaining the terrorism by providing financial support, weapons and explosives to terrorist groups", the statement said.