GENEVA, March 6 (Reuters) - The U.N. refugee agency said on Friday that nearly 100,000 people have been displaced within Lebanon and tens of thousands of Syrian refugees there have fled back over the border, calling the situation in the region a "major humanitarian emergency".

Israel has issued large-scale evacuation orders for southern Lebanon and parts of Beirut amid hostilities with the Iran-backed Lebanese group Hezbollah since a U.S.-Israeli air campaign against Iran began on February 28.

GENEVA, March 6 (Reuters) - The United Nations human rights chief will travel to Washington this month, he said on Friday, but expressed doubt he could influence the development of the Middle East crisis amid mounting concerns.

"I hope to go to Washington D.C. later this month, and we will see what this will bring," UN human rights chief Volker Turk told reporters in Geneva.

"We have obviously been in touch, but to be honest, I don't think it's in any way meaningful in terms of influencing the current trajectory," he added.

The United Nations on Friday demanded swift investigations into fatal Israeli strikes across Lebanon to decide if they complied with international law.

"Lebanon is becoming a key flashpoint," UN rights chief Volker Turk told reporters in Geneva.

"I call for an immediate cessation of hostilities."

Lebanon has been engulfed by the expanding Middle East war, after the Iran-backed group Hezbollah on Monday fired missiles at Israel to avenge the death of Iranian supreme leader Ali Khamenei.

BAKU, March 6 (Reuters) - Azerbaijan is evacuating its diplomats from Iran for their own safety, Foreign Minister Jeyhun Bayramov said on Friday, a day after Baku said four Iranian drones had crossed its border and injured four people in the Nakhchivan exclave.

Speaking at a news conference in Baku, Bayramov said that Azerbaijan was evacuating employees from its embassy in Tehran and its consulate general in Tabriz, the largest city in Iran's northwest, where many ethnic Azerbaijanis live.

By Olivia Le Poidevin

GENEVA, March 6 (Reuters) - Large-scale evacuation orders issued by the Israeli army for southern Lebanon and Beirut's southern suburbs raise serious concerns under international law, the U.N. human rights chief said on Friday.

"These blanket, massive displacement orders we are talking here about hundreds and thousands of people," said United Nations human rights chief, Volker Turk.

"This raises serious concern under international humanitarian law, and in particular when it comes to issues around forced transfer," he added.

By Olivia Le Poidevin and Emma Farge

GENEVA, March 6 (Reuters) - Key humanitarian air, sea and land routes are being constricted by disruption from the war in the Middle East, delaying life-saving shipments to some of the world's worst crises, 10 aid officials have told Reuters.

The U.S.–Israeli war on Iran entered its seventh day on Friday, convulsing global markets and disrupting supply chains with airspace closures and the halt of shipping through the critical Strait of Hormuz.

The United Nations rights chief called Friday for answers after a deadly strike on an Iranian elementary school, as a media investigation concluded the United States was most likely responsible.

On the first day of the war last Saturday, a strike hit an elementary school in the southern Iranian town of Minab and killed at least 150 people, say Iranian officials.

UN rights chief Volker Turk condemned "this absolutely tragic incident", and said he hoped investigations would be "prompt, and that they will be done in full transparency".

By Mohammad Yunus Yawar

KABUL, March 6 (Reuters) - Pakistani and Afghan troops exchanged fire at dozens of points along their border on Friday as the U.N. said their week-old conflict has forced the displacement of more than 100,000 people.

The South Asian nations show no signs of rapprochement in their worst fighting in years, adding to the volatility in a region also contending with U.S. and Israeli strikes on Iran - a nation that borders both Afghanistan and Pakistan.

Fresh Israeli strikes on Friday battered Lebanon, where Prime Minister Nawaf Salam warned "a humanitarian disaster is looming" due to mass displacement.

An Israeli strike on an office building in the southern city of Sidon killed five people and wounded seven, the Lebanese health ministry said, as Israel presses attacks on Lebanon's south, east, and in Beirut's southern suburbs.

Speaking to foreign ambassadors, the Lebanese premier said "the consequences of this displacement, at the humanitarian and political level, may well be unprecedented".

COPENHAGEN, March 6 (Reuters) - Maersk, one of the world's biggest container shipping groups, said on Friday it has temporarily suspended two services linking the Middle East to Asia and Europe as the Iran conflict continues to disrupt global supply chains.

The Danish group said in a statement it would halt its FM1 service connecting the Far East to the Middle East and its ME11 service linking the Middle East to Europe