(Updates death toll)

BAGHDAD, Dec 18 (Reuters) - A suicide bomber killed 16 people when he detonated a vest rigged with explosives in a Shi'ite Muslim village north of Baghdad on Tuesday, police said.

Suicide bombers, gunmen and car bombs killed 14 other people across the country. The violence coincided with an unannounced visit by U.S. Secretary of State Condoleezza Rice who lauded recent security gains in Iraq.

The worst incident was in the volatile Diyala province when a suicide bomber targeted a coffee shop in the al-Abbara village north of the city of Baquba, 65 km (40 miles) north of Baghdad. Twenty-eight people, including children who were near the site, were wounded in the blast, police said.

Also in Baquba, a suicide car bomber targeting a police checkpoint killed one policeman and one civilian, and wounded 15 people including three children, police said.

The U.S. military has said Sunni Arab al Qaeda gunmen are regrouping in Diyala province after being squeezed out of strongholds in Baghdad and the western Anbar province.

Police also said gunmen killed six men guarding oil pipelines near the city of Mosul. No damage to the pipelines was reported.

Attacks on Iraq's oil pipelines in the north are not uncommon. Earlier in December, a bomb fractured an internal pipeline linking oil fields in the city of Kirkuk to a storage and distribution point in northern Iraq.

In Baghdad, a car bomb killed four people including one policeman and wounded seven others in the city centre, police said. Gunmen also killed the dean of a private college in Baghdad near his home, they said.

An employee of a committee to purge members of Saddam Hussein's Baath party from public life was killed in Baghdad.

U.S. and Iraqi officials say violence across the country has dropped to its lowest levels in nearly two years, partly because of the deployment of 30,000 extra U.S. troops. U.S.-backed neighbourhood police patrols fighting al Qaeda and Shi'ite militias are also credited for the reduction in bloodshed. (Writing by Alaa Shahine; editing by Ross Colvin and Robert Woodward; Baghdad newsroom))

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