OSLO, May 4 (Reuters) - There were no signs of increased shipping traffic through the Strait of Hormuz on Monday, despite U.S. President Donald Trump announcing on Sunday that the United States would begin efforts to restore freedom of navigation there.

MarineTraffic data showed that only one tanker, a small, sanctioned liquefied petroleum gas carrier, a handful of cargo ships and a cable-laying vessel crossed the strait into the Gulf of Oman on Monday.

No other tankers or commercial vessels were spotted lining up to cross, and the German shipping group Hapag-Lloyd said that the passage of its ships remained impossible due to unclear safe passage procedures.

The US Central Command said it would begin on Monday to help restore freedom of navigation through the strait, while continuing its blockade of Iranian ports.

The Baltic Sea and International Maritime Council (BIMCO) stated that the shipping industry had not received any guidance regarding the US operation or its objectives, while the overall security situation remained unchanged.

Jacob Larsen, chief safety and security officer at Pimco, said, "Without Iran agreeing to allow commercial vessels to transit safely through the Strait of Hormuz, it is currently unclear whether the Iranian threat to shipping can be mitigated." Pimco provides security alerts to the industry.

The International Maritime Organization stated that hundreds of merchant ships and up to 20,000 sailors were unable to cross the waterway as a result of the Iranian war.

The US-led Combined Maritime Information Center said the maritime security threat level in the strait remains "serious" and advised mariners to consider taking a route through Omani territorial waters south of the maritime traffic separation system.

The US Central Command described the missions undertaken by the United States as "defensive" and said it would combine diplomatic efforts with military coordination.

Meanwhile, Iran warned the US Navy against approaching the Strait of Hormuz, stating that commercial vessels would need to coordinate with Iranian forces regarding any transit. It also released a new map outlining what it claimed was Iran's area of control.

Pakistan said it had received all 22 crew members of the Iranian-flagged container ship Tosca, who were detained by US forces last month, and that they would be transferred to their home countries.

The Pakistani Foreign Ministry also stated that the ship would be returned to its owners after repairs, describing the move as a "confidence-building measure."

The naval blockade imposed by the United States on Iranian ports on April 13 led to a decrease in Iranian oil exports.