Thailand police has retrieved a huge collection of weapons from a fugitive anti-junta leader's house, believing that it were to be used "to assassinate" the country's Prime Minister Prayuth Chan-ocha.

Police said that they found dozens of rifles, grenades and thousands of rounds of ammunition on Saturday (18 March) from a Pathum Thani house linked to red shirt leader Wuthipong Kochathamakun, who has been on the run since the military coup.

They also said that they arrested nine men in connection with the arms seizure, who they believe were trying to cause unrest.

"We found a rifle with a scope. We guarantee that this is not to shoot at birds but was going to be used to assassinate the leader of the country," National Police Chief Jakthip Chaijinda said on Sunday.

Kochathamakun belongs to the red shirt movement – a political group – which is loyal to exiled former prime minister Thaksin Shinawatra, who was ousted in the 2006 coup.

The activist group had led street rallies in 2009 and 2010 in support of the ex prime minister. Red shirt had also staged demonstration against the 2014 coup of former prime minister Yingluck Shinawatra – sister of Thaksin – whose government was overthrown by Prayuth, who was then the army chief.

Soon after the 2014 incident, the junta came to power and has since been trying to root out Thaksin's influence from the country. Prayuth's government has cracked down on a number of activists, journalists and dissidents in the process. Thai military has also banned political gathering of more than five people.

Police Chief Chaijinda said that they have not found any other proof of an assassination plot, but said Wuthipong and his group had always opposed the junta and posted on social media that the prime minister would be killed, Reuters said.

He added that the red shirt movement had also warned the officials that they would create unrest if the operations against an influential Buddhist temple continued.

The search operation at the Dhammakaya temple ended in February after police failed to find influential Thai monk – Phra Dhammachayo – wanted on charges of money laundering.