BAGHDAD, Oct 19 (Reuters) - A suicide bomber killed 19 at a funeral in Baghdad on Sunday as an ambush halted Iraqi forces' advance on a key northern city controlled by Islamic State fighters.
A suicide bomber killed 19 and wounded 28 others outside a Shi'ite Muslim mosque, where people were attending a funeral service, in western Baghdad, a police officer and medical official said.
"The attacker approached the entrance of the mosque and blew himself up among the crowd," the police officer said, speaking on condition of anonymity about the attack in the affluent neighborhood of Harthiya.
Baghdad has witnessed a surge in bombings in the last month, most of them claimed by Islamic State, as the government, headed by Prime Minister Haider al-Abadi, seeks traction in its effort to subdue Sunni parts of the country that Islamic State has seized this year.
Elsewhere, Iraqi forces attempted to retake the northern city of Baiji, which is adjacent to the country's largest refinery, which continues to be in the hands of the government despite a siege by Islamic State.
The military operation, launched in the early hours of Saturday, was snarled when an armored vehicle blew up near the security forces' convoy in a village some 20 km (15 miles) south of Baiji, officers said
The blast killed four soldiers and wounded seven.
"The attacker surprised our forces as he was driving a military armored vehicle. We thought it was our vehicle," said an army major participating in the operation.
"We are planning to retake Baiji as soon as possible to secure a key highway and to stop the daily attacks of terrorists on the Baiji refinery," he added.
The offensive looks to bypass the Iraqi city of Tikrit, which lies to the south of Baiji and is controlled by Islamic State, and instead to focus on Baiji itself.
Iraqi forces have protected the Baiji refinery since June despite being surrounded on all sides after the Iraqi army imploded in the north in the face of a major Islamic State military blitz.
The group holds territory across eastern Syria and northern and western Iraq, with the ambition of establishing rule based upon medieval Islamic precepts. The United States is leading an international coalition in conducting air strikes aimed to defeat the jihadists. (Reporting by Ahmed Rasheed, Ned Parker; Editing by Crispian Balmer and Susan Thomas)