Arsonists have set ablaze a pineapple farm owned by Burundi's President Pierre Nkurunziza, officials say.
The fire partially damaged the farm in the south-eastern Musongati area, they say.
The BBC's Prime Ndikumagenge in the capital, Bujumbura, says there have been several grenade and gun attacks in Burundi since Sunday.
The government blames the attacks on bandits, but many people are worried that a rebellion has resumed, he says.
About 300,000 people were killed in Burundi's 12-year civil war, which ended in 2005.
Tensions resurfaced during elections last year, with the opposition claiming the polls were marred by arrests, intimidation and vote-rigging.
Former rebel leader Agathon Rwasa withdrew from the presidential race and fled the country.
Mr Nkurunziza was the sole candidate in the poll.
Our reporter says that shortly before Mr Nkurunziza's farm was attacked, a school teacher who belonged to the ruling party was shot dead nearby.
He says grenade attacks have also taken place in south-west Burundi, and vehicles ambushed in the north.
The violence has killed at least six people, our reporter says.
No group has said it is responsible for the attacks.
Mr Nkurunziza, a former rebel leader from the majority Hutu ethnic group, took office in 2005 after a peace agreement with the Tutsi-dominated army.
Mr Rwasa - a hardline Hutu - initially refused to lay down arms.
He later formed a political party and signed a peace deal with Mr Nkurunziza's government in 2008.