Japan says it has not seen any evidence to prove a claim by the United States that Iran was involved in recent attacks on Saudi oil facilities.

“We are not aware of any information that points to Iran,” Japan’s Defense Minister Taro Kono told reporters at a briefing on Wednesday.

“We believe the Houthis carried out the attack based on the statement claiming responsibility,” he added, referring to the Yemeni group incorporated into the armed forces fighting back a Saudi-led war on Yemen.

Kono further said Japan would not participate in any potential military action against Iran due to constitutional restraints and would instead pursue a diplomatic solution to the current tensions in the region.

The Yemeni military, which also comprises of members of the Houthi Ansarullah movement, targeted Abqaiq and Khurais oil facilities run by the Saudi state-owned oil company Aramco before dawn on Saturday.

The attacks knocked out more than half of the Saudi crude output, or five percent of the global supply.

US officials soon claimed that the attacks had originated from inside Iran.

Iran has rejected the accusation and said the attacks were a legitimate act of self-defense by Yemen, which has been under incessant strikes by the Saudi-led coalition since 2015. The US is a member of that invading coalition.

After the attacks on the Saudi oil facilities, President Donald Trump said the US was “locked and loaded” for a response at the behest of Saudi Arabia, although he later said that he wanted no conflict with any country. Still later, the Pentagon reportedly prepared “response” options for the US president.

Meanwhile, Yemen’s Houthi Ansarullah movement, which claimed responsibility for the attacks shortly after conducting them, has warned Saudi Arabia that targets “will keep expanding” if the Saudi-led war on Yemen continues.

Saudi Arabia and a number of its regional allies launched the war on Yemen in March 2015, with the goal of bringing a former regime to power.

Yemeni forces have been hitting targets inside Saudi Arabia in retaliation.

The US-based Armed Conflict Location and Event Data Project (ACLED), a nonprofit conflict-research organization, estimates that the Saudi-led war has claimed more than 91,000 lives over the past four and a half years.

The war has also taken a heavy toll on Yemen’s infrastructure, destroying hospitals, schools, and factories. The UN says over 24 million Yemenis are in dire need of humanitarian aid, including 10 million suffering from extreme levels of hunger.