* Ships carrying Saudi crude for China and India heading to

Suez Canal

* U-turns suggest more potential disruption to a major

shipping route

* Yemen's Houthis declared a blockade against Saudi Arabia

on Monday

By Florence Tan and Nidhi Verma

SINGAPORE/NEW DELHI, July 21 (Reuters) - Three oil tankers

loaded with Saudi crude for China and India made U-turns in the

Red Sea on Tuesday, heading towards the Suez Canal rather than

braving the Yemeni coast at the sea's mouth following a warning

from Yemen's Iran-aligned Houthi militia.

The changes in direction by the ships, the Xin Long Yang, the

Rodos and the Amazon, suggest a second potential disruption to a

major shipping route that could compound the shortfall in global

energy markets caused by the closure of the Strait of Hormuz.

The Houthis on Monday declared a naval blockade against

Saudi Arabia, opening a potential new front in the U.S.-Israeli

war with Iran and raising the threat to global energy supplies

and trade beyond the Gulf.

The group, in an email sent to shipping companies, warned them

not to load or discharge cargo at Saudi Arabian ports and said

such activity may result in being targeted "in any location".

The Houthis control northern Yemen, including the coast of

the Bab el-Mandeb, the strait at the mouth of the Red Sea. Since

the Strait of Hormuz controlling access to the Gulf has been

blocked during the war, Saudi Arabia's Red Sea port of Yanbu has

become the main alternative route for Middle East oil, allowing

exports of millions of barrels per day.

War risk insurance costs have already risen in the past 24 hours

with risk assessments for Saudi ports being re-evaluated,

insurance industry sources said on Tuesday.

"Vessels calling at Saudi Arabian ports are advised to

reconsider transiting the Red Sea and to consider implementing

enhanced mitigation measures," British maritime security company

Ambrey said, adding that it assessed vessels calling at Saudi

Arabian ports "were at high risk".

U-TURNS AT SEA

The Xin Long Yang, a Very Large Crude Carrier which

completed the loading of 2 million barrels of Saudi crude at

Yanbu on Monday, was originally heading to exit the Red Sea to

go to China, but made a U-turn and was heading to Suez instead,

shipping data showed.

The smaller tanker Rodos, which had loaded about 700,000 barrels

of Saudi crude for India, also made a U-turn for Suez on

Tuesday, according to the data. The Suezmax tanker Amazon, which

loaded crude on Tuesday for India, also headed to Suez. The

tankers switched off their transponders on Tuesday.

Dynacom Tankers Management, which manages Rodos and Amazon, and

Cosco Shipping, manager of Xin Long Yang, did not immediately

respond to requests for comment.

Another VLCC, New Prime, which was scheduled to arrive at

Yanbu later this week to load crude, has also turned back off

Oman before entering the Red Sea. Its manager Associated

Maritime Co HK did not respond to a request for comment.

Three shipping sources said Yanbu was still operating to load

oil onto ships that were already in the Red Sea or arriving via

Suez. Ship tracking data showed a tanker, the Olympic Luck,

which had passed into the Red Sea through Suez, was still

heading for Yanbu, as were several ships that were already close

by. However, most tankers sailing in the Red Sea or loading at

Yanbu port have switched off their transponders since Tuesday.

But forcing tankers to use the Suez Canal rather than exit

the Red Sea through the Bab el-Mandeb would add weeks to

shipments to customers in Asia, requiring sailing through the

Mediterranean and around Africa.

"While an actual blockade seems unlikely given the resources

required for such an undertaking, a step-up in hostilities could

see Houthis targeting Saudi-associated ships transiting the Bab

el-Mandeb strait," ship broker Clarksons said in a note on

Tuesday.

In recent months on average 10 crude tankers have sailed

through the Bab el-Mandeb daily.

"However, should Houthis affect traffic through the region,

we could see a reshuffling of crude cargoes in which Yanbu

volumes are increasingly directed towards Europe."

Fully laden VLCCs transiting the canal must first unload

some of their oil, which can bypass the canal by being pumped

through the SUMED pipeline to the Mediterranean.