Iran has started installing high-tech machines at its main uranium enrichment site that are capable of accelerating activity that can produce reactor fuel and — with further upgrading — the core of a nuclear warhead, Western diplomats said Wednesday.

Iran already said last week that it had begun installation, but diplomats said at the time the announcement was premature, with the enriching centrifuges on site but not yet being put into place

However, three diplomats speaking to The Associated Press in Vienna on Wednesday said installation was well on its way, with 100 or more machines already mounted. They demanded anonymity because they were not authorized to divulge confidential information.

Iran denies any interest in nuclear weapons and says it is enriching only for nuclear power, science and medical purposes.

Nigerian terror group linked to Iran

In another development, Nigeria's secret police said Wednesday they broke up a terrorist group backed by "Iranian handlers" who wanted to assassinate a former military ruler and gather intelligence about locations frequented by Americans and Israelis.

The State Security Service, responsible for domestic spying in Africa's most populous nation, offered no details about who actually controlled and bankrolled the group. However, a spokeswoman said it had arrested three suspected terrorists, including the group's leader, before they could launch attacks.

The leader's "lieutenants successfully conducted surveillance and gathering relevant data … [for] possible attacks," Marilyn Ogar said. "He personally took photographs of the Israeli culture centre in Ikoyi, Lagos, which he sent to his handlers."

The service identified the leader as Abdullahi Mustaphah Berende, 50, leader of a local Shia sect in Ilorin. Ogar said Berende was arrested along with two other suspected members, while another remains at large.

Berende travelled to Iran in 2006 and studied at an Islamic university, Ogar said. He returned in 2011 and learned how to use Kalashnikov assault rifles and pistols, as well as making and detonating homemade explosives, she said.

Ogar identified high-level targets of the group as former military ruler Ibrahim Babangida and Ibrahim Dasuki, a former Sultan of Sokoto, a major Islamic leader in the nation. The group also conducted surveillance on USAID, the U.S. Peace Corps and other targets, she said.

Accused linked to cash payment

Berende also received about $30,000 US in cash to fund the group's planned operations.

Ogar did not take questions, nor did she elaborate on the statement. It remains unclear how close the group was to conduct an attack.

Nigeria, home to more than 160 million people, is largely divided into a Christian south and a Muslim north. Nigeria's Muslims are predominantly Sunni, though there is a Shiite community in the country. Iran has backed Shia groups in Nigeria in the past.

In 2010, authorities at Apapa Port in Lagos found 107mm artillery rockets, rifle ammunition and other weapons from Iran hidden in a shipment supposedly bound for Gambia. A Nigerian and an Iranian with alleged ties to the country's Revolutionary Guard face criminal charges in that case.