Former Director of the Central Intelligence Agency John Brennan condemned the killing of an Iranian scientist believed to be linked to Tehran’s nuclear program Friday, calling it “criminal” and “highly reckless.”

Details on the attack remain slim, but local outlets have reported that Mohsen Fakhrizadeh was killed after a truck full of explosives concealed, by a pile of wood pulled alongside the scientist’s sedan before detonating in the town of Absard, located just east of Tehran.

“This was a criminal act & highly reckless,” Brennan wrote on Twitter Friday afternoon. “It risks lethal retaliation & a new round of regional conflict.”

Iran’s foreign minister said that attack on Fakhrizadeh had “serious indications” that Israel was involved in the assassination but did not provide additional details – though there are expected to be international repercussions.

Fakhrizadeh’s assassination comes less than a year after Gen. Qassem Soleimani was targeted by the U.S. military in a drone strike, killing one of Iran’s topic officials and pushing U.S.-Iran relations to the brink after Iran vowed retaliation.

“Iranian leaders would be wise to wait for the return of responsible American leadership on the global stage & to resist the urge to respond against perceived culprits,” Brennan wrote, urging Iranian officials to address the topic diplomatically once President-elect Joe Biden’s administration takes over the White House.

Trump has yet to publically comment on the attack, but retweeted a message by Israeli journalist Yossi Melman who said the killing of the Iranian nuclear scientist was “a major psychological and professional blow for Iran.”

No one has yet claimed responsibility for the death of Fakhruzadeh, who died in the hospital, but Iranian Foreign Minister Mohammad Javad Zarif said it was an act of “state terror.”

“Terrorists murdered an eminent Iranian scientist today. This cowardice — with serious indications of Israeli role — shows desperate warmongering of perpetrators,” Zarif said on twitter.

“Iran calls on int'l community—and especially EU—to end their shameful double standards & condemn this act of state terror.”

Fakhruzadeh supposedly ran Iran’s AMAD nuclear program, which was supposed to have been terminated in 2003, though Israel and other western nations suspected its resurgence.

CLICK HERE TO GET THE FOX NEWS APP 

Iran has long maintained its nuclear program is strictly for civilian services like generating electricity.

Iran and its nuclear sites are monitored by the International Atomic Energy Agency, though under the Trump administration, the U.S. has maintained a continued suspicion that Iran has continued to develop their nuclear capabilities.

The Associated Press contributed to this piece.