BAGHDAD -- Iraq has executed nearly 100 people so far this year, a big increase over previous years that has intensified concern about whether defendants are receiving fair trials in a country where the United States has spent billions of dollars trying to reform the judicial system after decades of dictatorship.

The government says most of the executed had been convicted of terrorism as bombings and shootings persist in Iraq, albeit not at the levels at the height of its conflict years ago. However, international observers worry that the legal process is faulty and that some trials are politically motivated -- including this month's death sentence against Iraq's fugitive Sunni vice-president, Tariq al-Hashemi, a longtime foe of Shiite Prime Minister Nouri al-Maliki who was convicted in absentia of running death squads.

The executions in 2012 of at least 96 people, all by hanging, amount to more than a quarter of all convicts who have been put to death in the last eight tumultuous years under leaders who struggled to stabilize a country at war after dictator Saddam Hussein was ousted in the U.S.-led war.

Christof Heyns, the U.N. investigator on arbitrary executions, described the government-sanctioned executions as "arbitrary killing" that is "committed behind a smokescreen of flawed legal processes." He warned that the " continued lack of transparency about the implementation of the death penalty in Iraq, and the country's recent record, raise serious concerns about the question of what to expect in the future."

He made the remarks in a statement in August after more than two dozen people were executed in one week.

Since 2005, Iraq's government has executed 372 people, including at least nine women and number of foreigners convicted of terror charges, according to Justice Ministry data. The number of foreigners among those killed this year was not available.

In the last month alone, the government executed 26 people, including a Saudi, a Syrian and three Iraqi women. The executions were announced with no details about the names or trials of those who were killed, drawing widespread international denunciation.

Haider al-Saadi, the spokesman for the Iraqi Justice Ministry, said the death penalty is the best way for the Iraqi government to ease the suffering of the victims' families.

"The criminals in Iraq are not like the ones in Switzerland or other European Union countries or any others," he said. "Iraq today is facing the most dangerous terrorists in the world."

Iraqi courts have issued 867 death sentences since 2004, with most of them still on death row. The most prominent Iraqi to be executed since Saddam's fall was the dictator himself, hanged on Dec. 30, 2006, for his role in the 1982 killings of 148 Shiites following a failed assassination attempt in the early 1980s. A handful of his senior henchmen followed him to the gallows.

After the U.S.-led invasion in 2003, coalition authority officials suspended Iraq's death penalty, which Saddam and his Sunni regime had used to get rid of his opponents in the majority Shiite country. Shiites have led Iraq since, and in 2004 the transitional government reinstated capital punishment. Now, the government is showing increasing enthusiasm for the death penalty as a law-and-order tool.

Iraq was ranked fourth among the top five executioners in the world in 2011, according to London-based Amnesty International. It said most of those who were put to death were convicted of murder, kidnapping, rape and other violent crimes. China is on the top of the list, with thousands of people believed to be executed each year, followed by Iran and Saudi Arabia. The U.S. was ranked fifth.

Amnesty said the people executed in Iraq were sentenced in courts that "failed to meet international fair trial standards." It accused Iraq of issuing convictions in at least some cases that were based on torturing or otherwise coercing witnesses into giving statements against the accused. It has also said that some defendants were sentenced after trials that lasted just a few minutes.

U.S. auditors estimate American taxpayers have spent about $10 billion since 2003 to rebuild and strengthen Iraq's justice system after decades of Saddam's abuse.

Abdul-Sattar Bayrkdar, the spokesman for Iraq's Supreme Judicial Council, defended Iraqi courts as independent and immune to political pressures.

"We have a law and all our judges work according to it. All the trials and proceedings are according to the international law," he said. He added that "some" of the criticism is politically motivated and that "such allegations need proof."

Earlier this month, a Baghdad court found al-Hashemi, the vice-president, guilty of masterminding the murders of an Iraqi lawyer and a security official -- killings that the government has described as among at least 150 bombings, assassinations and other attacks by his henchmen. He was sentenced to death by hanging. Al-Hashemi is living in exile in Turkey and has denied charges that he says amount to a political vendetta by his archenemy, the prime minister.

Baghdad-based political analyst Khadhum Muqdadi said Iraq's government has embraced the death penalty in recent years as a way to show the country is aggressive about going after terrorists, even though it fails to prevent the daily violence that has killed hundreds each month.

The government "has failed to dry up the sources of terrorism, to stop the attacks and to achieve security," Muqdadi said. "With these executions, it is trying to ease the pressure it is facing from the public opinion because of its failure to maintain security."