Devi Asmarani, Jakarta – Is that a rice cooker or a bomb in the shopping bag? Bomb paranoia has struck Jakarta and other major cities as residents are scared stiff at the sight of unattended bags, boxes and odd-looking items after the latest spate of explosions to rock the country.

With two explosions and two foiled bombing attempts at busy nightspots here on Sunday, Indonesians are not taking chances anymore.

Mr Muhtamil, 24, found this out the hard way. He lost his newly bought Magic Jar cooking appliance to a panic-stricken mob minutes after he left it in the care of a cigarette kiosk owner.

Kiosk owner Yusuf said: "All of a sudden, people were panicking and didn't dare to open the box even though it says 'Magic Jar'." Fearing the box would explode, the mob tied it to the end of a long pole and carried it nervously across the busy Gajah Mada street before dumping it into the Ciliwung river. When Mr Muhtamil returned to the kiosk, he was taken to the police station for questioning.

Several similar "bomb discoveries" have also been reported. Most of the items were either thrown into a safer place – a dumpster or a creek – as quickly as possible, or dissected by the bomb squad.

One "suspicious-looking" black suitcase found in front of a house in Pulogadung, East Jakarta, on Tuesday night was blown up by the bomb squad. Instead of bomb fragments, officers found pieces of documents and car keys. The suitcase appeared to have been stolen and later abandoned by thieves.

Mr Roni, a parking attendant at a Central Jakarta shopping centre, said: "I have become very nervous when I stand near a parked car. Often, I wonder if there is a bomb somewhere inside or under it."

The bomb paranoia may have been encouraged by the police themselves. On Monday, they told the public to "report any suspicious items, especially petrol containers painted in stripes". The explosives found on Sunday were crudely assembled and placed inside such containers.

The police said the paint was an effective way to conceal fingerprints on the container. Over the last two years, explosives have been disguised in many ways. Some were in biscuit tins which were sent to churches as Christmas parcels.

A pastor at a Pentecostal church in Central Jakarta said: "We're very strict about accepting packages or parcels now – nothing gets opened inside or near the church." But not all recent "bomb discoveries" were false alarms.

Yesterday, a grenade was found in a vacant house in Kebayoran Baru, South Jakarta. On Wednesday, residents in North Surabaya found similar grenades in a waste disposal near a busy market. All the grenades were defective.

Police are calling on the public to remain calm, saying they have deployed 100 extra patrol cars in Jakarta for added security.