Burundi police said on Friday eight people had been arrested for planning attacks to disrupt a constitutional referendum next month that could keep President Pierre Nkurunziza in power until 2034.Police spokesperson Pierre Nkurikiye said security forces on Thursday morning discovered two automatic weapons and ammunition during a "search and seizure" operation at the home of a suspect in western Burundi."Our investigation resulted in the arrest of seven more people, eight in total, who shared the goal of disrupting the next referendum with the use of firearms," he said.The eight suspects were displayed to journalists in the capital Bujumbura on Friday, along with the alleged evidence.Nkurikiye said investigations were underway to find "who is behind this criminal movement" warning that there were "some politicians who have already expressed through the media their intention to disrupt this referendum by any means, including weapons."A draft constitutional amendment, proposed in October and allowing Nkurunziza, 54, to stand for two more seven-year terms from 2020, is due to be voted on in May.The government has accused exiled oppositionists, and neighbouring countries, of planning to undermine the referendum and has deployed military units to areas bordering Rwanda to the north and the Democratic Republic of Congo to the west.Patrols by the ruling party's youth wing the Imbonerakure - described as a militia by the UN - have also increased.Nkurunziza's run for a controversial third term in 2015 plunged Burundi into a deep political crisis that has left at least 1 200 people dead and forced 400 000 to flee the country. The International Criminal Court (ICC) has begun an investigation into widespread abuses since then.Earlier this week US-based Human Rights Watch said government forces and ruling party members - including the Imbonerakure - were targeting suspected opponents ahead of the May 17 referendum.Burundi's lower house late on Wednesday voted to allow security forces in the politically tense nation to conduct night raids without a search warrant.The bill must now go before the Senate before being passed into law by President Pierre Nkurunziza "as fast as possible", a senior member of the ruling CNDD-FDD party told AFP, asking not to be named.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.