* Brent crude futures up 6%

* European shares fall

* Concerns over Mideast ceasefire grow

(Updates throughout)

By Sophie Kiderlin

LONDON, April 20 (Reuters) - Oil prices jumped and

global equities eased on Monday as markets grew increasingly

concerned that the ceasefire between the U.S. and Iran might not

hold, while tensions over the Strait of Hormuz escalated.

Brent crude futures rose about 6% to $95.85 a

barrel. MSCI's world share index was last down

around 0.3%, with Europe's cross-regional STOXX 600

down 1.1%, after Asia's equity markets shrugged off risks to

advance. S&P 500 futures were 0.65% lower.

Concerns grew on Monday that the ceasefire between the

United States and Iran might not hold after the U.S. said it had

seized an Iranian cargo ship that tried to run its blockade and

Iran vowed to retaliate.

The U.S. has maintained a blockade of Iranian ports, while

Iran has lifted and then reimposed its own blockade on marine

traffic passing through the Strait of Hormuz. Kpler data however

showed that more than 20 vessels carrying oil products, metals,

gas and fertiliser passed through the strait on Saturday, the

busiest day for the chokepoint since March 1.

"Markets try to cling on to every bit of news that may point

to one outcome or another, hence these large swings. But it is

still a very uncertain and volatile situation," Sandra

Horsfield, economist at Investec, said.

She noted that while markets have pulled back, moves made

Friday - when Iran said it would open the Strait of Hormuz - had

not been fully retraced, suggesting that at least some "improved

sentiment still prevails".

Outside the Middle East, British Prime Minister Keir Starmer

is slated to address Parliament on Monday, facing calls for his

resignation over his handling of the appointment of Peter

Mandelson as U.S. ambassador even though he had failed a vetting

process.

PEACE TALKS IN QUESTION; FOCUS ON HORMUZ

Meanwhile, the outlook for further negotiations between the

U.S. and Iran seemed uncertain.

"Whether this impasse proves to be merely a detour on the

path to a resolution remains to be seen, but more volatility

would seem the most likely outcome," Derren Nathan, head of

equity research at Hargreaves Lansdown, said in a note.

Iran rejected new peace talks with the U.S., its state news

agency reported on Sunday, hours after U.S. President Donald

Trump said he was sending envoys for talks in Pakistan and would

launch new strikes on Iran unless it accepts his terms.

"We always thought there would be some swings and

roundabouts within that, rather than a straight linear path to

the end outcome," said Investec's Horsfield.

Bonds, which rallied on Friday, retreated and the yield on

benchmark 10-year Treasuries rose 2.6 basis points to 4.2697%,

while the yield on German 10-year government bonds was last 3.6

bps higher at 3.0015%.

The dollar - which was sold for the best part of the past

two weeks - broadly steadied, trading at $1.1761 per euro.

Wall Street indexes touched record highs on Friday,

supported by expectations of robust first-quarter earnings, the

bulk of which come this week.

British inflation data, U.S. retail sales and European

Purchasing Managers' Index figures are also due through the

week, though much of markets' focus will be on Gulf shipping.

"The critical barometer of geopolitical risk has been

distilled into one data point: The number of ships transiting

the Strait of Hormuz," said Bob Savage, head of markets macro

strategy at BNY.

"Peace talks matter, but the immediate focus is on oil and

other supply shortages driving inflation."