London — Britain on Monday urged Iran to stop sending weapons into Yemen and instead use its influence to end the conflict. The United Nations has found Tehran in violation of an arms embargo on Yemen by failing to block supplies of missiles and drones to the Huthis. In a joint statement, Britain's Foreign Secretary Boris Johnson and International Development Secretary Penny Mordaunt urged Iran to change course. If Iran is genuinely committed to supporting a political solution in Yemen -- as it has publicly stated -- then it should stop sending in weapons which prolong the conflict, fuel regional tensions, and pose threats to international peace and security, they said in the statement. We question why Iran is spending significant revenue in a country with which it has no real historical ties or interests, rather than using its influence to end the conflict for the good of the Yemeni people. Johnson and Mordaunt said: We support the Saudi-led coalition's efforts to restore legitimacy in Yemen, as accepted by the UN Security Council. A watchdog group said on Monday that roadside bombs disguised as rocks in Yemen bear similarities to others used by Hezbollah in southern Lebanon and by insurgents in Iraq and Bahrain, suggesting at the least an Iranian influence in their manufacture. The report by Conflict Armament Research comes as the West and United Nations researchers accuse Iran of supplying arms to Yemen's Shiite rebels Houthis. Those weapons included ballistic missiles used to target Saudi Arabia. What we're hoping this does is make plausible deniability not very plausible, said Tim Michetti, head of regional operations for Conflict Armament Research. You can't really deny this anymore once the components these things are made with are traced to Iranian distributors. Michetti's organization, an independent watchdog group, said it examined a fake rock bomb in January near Mokha, some 250 kilometers (150 miles) southwest of the capital, Sanaa. The fiberglass-encased bomb, packed with explosives, could be armed by radio and triggered by an infrared beam, the group said. It said there were three varieties, including anti-personnel mines and so-called explosively formed projectiles, which can penetrate armored vehicles and were used with lethal effect against US troops following the 2003 invasion of Iraq. Electrical circuitry in the bombs mirrored those manufactured by militants in Bahrain, while the bombs bore markings suggesting one workshop mass-produced the explosives, the report said. Such bombs, however, have yet to be used in Bahrain. Investigators also found a type of Chinese-manufactured wire covering used in other Iranian materiel, the report said. It said independent experts also examined the explosives. Those experts said that construction indicates that the bomb maker had a degree of knowledge in constructing devices that resembled, and possibly functioned in a manner similar to (explosively formed projectile bombs) that have been forensically tied to Iran and Hezbollah, the report said. This is not the first time Iran has been accused of arming the Houthis. The US Navy's 5th Fleet, based in Bahrain, has repeatedly said Iran sends arms into Yemen. It points to seizures over a four-week period in early 2016, when coalition warships stopped three dhows, traditional ships that ferry cargo in the Persian Gulf. The dhows carried thousands of Kalashnikov assault rifles as well as sniper rifles, machine guns, rocket-propelled grenade launchers, anti-tank missiles and other weapons. One dhow carried 2,000 new assault rifles with serial numbers in sequential order, suggesting they came from a national stockpile, a previous Conflict Armament Research report said. The rocket-propelled grenade launchers also bore hallmarks of being manufactured in Iran, the group said. The group has also said drones used by the Houthis to crash into Patriot missile batteries in Saudi Arabia share near-identical design and construction characteristics of Iranian drones. The weapons transfers also allegedly include ballistic missile technology. The United Nations, Western countries and the Saudi-led coalition fighting in Yemen all say the Houthis' Burkan or Volcano missile mirrors characteristics of an Iranian Qiam ballistic missile. They say that suggests Tehran either shared the technology or smuggled disassembled missiles to the Houthis who then rebuilt them. — Agencies