BAGHDAD, Iraq – Insurgents carried out two dramatic ambushes yesterday, killing 11 people including two American civilians in a roadside bombing in Basra and an attack on an Iraqi convoy in Baghdad.

Meanwhile, Iraqi officials expressed hope that American hostage Jill Carroll would eventually be released, and kidnappers freed the sister of Iraq’s Interior Minister after holding her hostage for two weeks.

The ambushes, in which gunmen also seized two Kenyan engineers, were part of a surge in violence that left scores of Iraqis dead across the country yesterday.

In the most gruesome development, police said militants used this week’s downing of an American helicopter to carve out a killing field north of Baghdad, slaying more than 40 people on remote roads that Iraqis were forced to use after American troops cordoned off the crash zone.

Thirty people were dragged from their cars yesterday at crude checkpoints erected on unpaved roads and shot dead execution-style in farming areas in Nibaei, a town near Dujail, about 50 miles north of Baghdad, police Lieutenant Qahtan al-Hashmawi said.

Since Monday’s crash of an American Army AH-64 Apache helicopter that killed its two pilots near Mishahda, 25 miles north of Baghdad, American and Iraqi forces cordoned off a large section of the main road near Dujail, police and eyewitnesses said.

More than a dozen other Iraqis died yesterday in attacks linked to the insurgency.

The increased violence came as authorities prepare to announce the results this week of the December 15 election. American and Iraqi officials expect more attacks as religious and ethnic groups jockey for power in the new government.

In the boldest attack, gunmen opened fire on a convoy of the mobile telephone company Iraqna, killing six security guards and three drivers in the Nafaq al-Shurta district of western Baghdad.

The chairman of the Egyptian communications firm that controls Iraqna, Naguib Sawiris, said the attackers seized the two Kenyans.

The two American civilians were killed in a roadside bombing in the southern city of Basra. They worked for the Texas-based security company Dyn-Corp and were training Iraqi police. A third American was seriously wounded in the attack, the American Embassy said.

An Associated Press photographer at the scene said two four-wheel-drive vehicles were targeted. The area was surrounded by heavily armed British forces, whose main base in Iraq is in Basra.

The killings occurred as a joint American-Iraqi investigation was under way to find Ms. Carroll, the 28-year-old American journalist who was abducted January 7 in Baghdad. The freelance reporter for the Christian Science Monitor was seen in a video aired Tuesday by Al-Jazeera television.

Al-Jazeera said the silent 20-second video included a threat to kill Ms. Carroll in 72 hours unless American authorities release all women detainees in Iraq. American officials said eight women were in security detention and none had been freed as of last night.

Nevertheless, a deputy interior minister, Major General Hussein Kamal, spoke hopefully about prospects for Ms. Carroll’s release.

“Efforts are continuing to find the American journalist,” he said. “We cannot say more because of the sensitivity of the matter, but God willing, the end will be positive.”

President Bush ignored shouted questions yesterday about what his administration is doing to find Ms. Carroll. A White House spokesman, Scott McClellan, said her safe return was a priority for the administration” but refused to say more “because of the sensitivity of the situation.”

The Washington bureau chief for the Christian Science Monitor, David Cook, said at a news conference yesterday that Ms. Carroll’s work has demonstrated she is respectful of Arab culture and people, and the newspaper has shown it treats different cultures and viewpoints fairly.

He did not answer directly whether the newspaper was involved in any negotiations for her release but told reporters: “the Monitor is undertaking strenuous efforts on Jill’s behalf … taking advantage of every opportunity we have at our disposal.”

Insurgents in Iraq have kidnapped more than 240 foreigners and killed at least 39 of them. Hundreds, perhaps thousands, more Iraqis have been abducted either by insurgents or gangs seeking ransoms.

Yesterday, the sister of Interior Minister Bayan Jabr was released and was at home, a secretary to Mr. Jabr, Ali al-Khaqani, said. He refused to give details, including her name, when she was released or whether ransom was paid. She was abducted January 3 in an attack in which a bodyguard was killed.

Also yesterday, Iraqi officials confirmed that 35 men rejected for membership in the Iraqi police were abducted Monday by masked gunmen who stopped their bus en route from Baghdad to Samarra north of the capital.

An American soldier based in Baghdad died of non-combat-related wounds Tuesday, the military said. At least 2,221 members of the American military have died since the beginning of the war in 2003, according to an AP count.