(Refiles to wider audience with no changes to text or headline)

By Ted Hesson, Jonathan Allen and Rich McKay

WASHINGTON, March 13 (Reuters) - U.S. law enforcement officials are on heightened alert as the Iran war enters its third week, but the limits of their vigilance were on display as seeming lone-wolf attacks unfolded more than 500 miles apart in Virginia and Michigan on Thursday alone.

The Pentagon's engagement with the media during the Iran war has been heavy on rhetoric, short on operational detail and characterized by an adversarial approach to mainstream outlets that seek to raise questions about the conflict.

While journalists had access to detailed, often-daily briefings as well as embeds with troops during previous wars such as those in Iraq and Afghanistan, the US military has taken a markedly different approach to communicating during the Iran conflict.

By Lisa Baertlein

LOS ANGELES, March 13 (Reuters) - Two explosive-laden, unmanned boats rammed the Safesea Vishnu tanker in an Iraqi seaport on Wednesday, sparking a fiery blast that engulfed the vessel's port side in flames and left crew only seconds to react, according to an early assessment conducted by the vessel's U.S. owner and operator.

"After speaking to the surviving crew members, the attack appears to have been deliberate and calculated," New Jersey-based Safesea Group said in a statement.

By Jasper Ward

WASHINGTON, March 13 (Reuters) - A top United Nations humanitarian official on Friday called for humanitarian aid to be allowed to pass safely through the Strait of Hormuz amid the U.S.-Israeli war on Iran.

The comments made by Tom Fletcher, the U.N. under-secretary-generalfor humanitarian affairs and emergency relief coordinator, comes as Iran threatens to close the strait, which is considered a key trade route.

By Ryan Patrick Jones

March 13 (Reuters) - The United States is offering a reward of up to $10 million for information about senior Iranian military and intelligence officials, including its new Supreme Leader, Ayatollah Mojtaba Khamenei.

The reward targets 10 officials associated with Iran's Islamic Revolutionary Guard Corps (IRGC), according to the State Department website. The military force, created after Iran’s 1979 Islamic Revolution, is loyal to the supreme leader and tasked with protecting the Shi’ite clerical establishment.

By Alexander Cornwell and Maya Gebeily

TEL AVIV/BEIRUT, March 13 (Reuters) - Israel destroyed a bridge in southern Lebanon on Friday and dropped leaflets in Beirut threatening Gaza-scale devastation as it deployed more troops to fight Iran-backed Hezbollah and warned of more attacks on the country's infrastructure.

As Israeli warplanes pounded Beirut's suburbs with air strikes, Lebanon's interior minister said authorities were unable to accommodate the hundreds of thousands of people who have sought refuge in the capital.

OSLO, March 13 (Reuters) - Three brothers and their mother have been remanded in police custody for up to four weeks on suspicion of taking part in the bombing of the U.S. embassy in Oslo last week, a Norwegian court said in a ruling on Friday.

The U.S. embassy was hit by an explosion on Sunday and police later said they had apprehended the suspects, accusing them of a "terror bombing" intended to kill or cause significant damage.

By Phil Stewart and Idrees Ali

WASHINGTON, March 13 (Reuters) - The U.S. military said on Friday it has elevated the investigation into a devastating February 28 strike on an Iranian girls' school after media reports revealed the probe shows U.S. forces were likely responsible.

Iran has said thestrike on the Shajareh Tayyebeh School killed 168 children. If U.S. fault is confirmed, it would rank among the worst incidents of civilian deaths in decades of U.S. military strikes in the Middle East.

Reuters first reported the investigation's initial findings on March 5.

The war in the Middle East has largely paralysed the Gulf region's crucial oil industry, which has been hit by attacks and an export blockade.

The war has forced companies to dramatically slow or even halt production -- and restarting it will not be easy, even when the war is over.

- What has been targeted? -

Since the war started with US-Israeli strikes on Iran on February 28, at least 33 strikes or attempted strikes have targeted energy infrastructure in the Middle East, according to an AFP tally.

The US-Israeli air strikes that on February 28 killed Ayatollah Ali Khamenei not only resulted in the death of Iran's longstanding supreme leader but also several key family members.

His son Mojtaba, one of Khamenei's six children, was a week later named the new supreme leader. Other key family members were however killed, even though there has been uncertainty about the fate of some.