Tehran, Iran (CNN) -- The United States is urging the Iranian government to halt executions after Tehran hanged a Dutch-Iranian woman, saying she was a drug smuggler.
The International Campaign for Human Rights in Iran has said the drug charges were only a pretext to execute Zahra Bahrami, and the Netherlands froze all ties with Iran on Sunday, a day after the hanging.
On Monday, the U.S. State Department said it was "deeply concerned that Iran continues to deny its citizens their human rights."
"Judicial cases, trials, and sentences continue to proceed without transparency and the due process rights enshrined in Iran's own constitution," it said.
The department said it was especially troubled by Bahrami's execution, saying she was denied access to Dutch consular officials.
"Her execution is one of dozens carried out in recent weeks amid serious questions about the motives of the Iranian government," it said.
Iran trails China in the number of executions worldwide, according to Amnesty International.
Iran hanged Bahrami on Saturday, saying she was a drug smuggler, the semi-official Fars news agency reported, although the Dutch government expressed "great concern" about her case three weeks ago.
Fars said Bahrami smuggled cocaine into Iran with the help of a Dutch partner.
But the International Campaign for Human Rights in Iran said Bahrami was originally charged with security offenses in the wake of widespread protests against the government over a controversial presidential election in June 2009.
Her lawyer was "shocked" to find she had been hanged, the group said.
"I was absolutely not informed about this. They should have informed her lawyer of the execution, but I had no idea. I don't know what to say. Just that I am shocked," Jinoos Sharif Razi told the group.
The campaign said it learned of the hanging from Bahrami's daughter.
Bahrami was accused of bringing cocaine into the country twice and selling it. Cocaine and opium were found during a search of her house, Fars reported.
Her sentence also included 70 lashes and a $1,400 fine, Fars reported.
Fars added that during a search of her house, while she was charged with security crimes, 450 grams of cocaine and 420 grams of opium were discovered and, following further investigation, it was found that she had also distributed 150 grams of cocaine.
Iran denied Bahrami access to Dutch consular assistance and would not let Dutch officials attend her trial because Tehran did not recognize her dual citizenship, the Ministry of Foreign Affairs in the Netherlands said on January 5.
CNN's David Wilkinson contributed to this report.