A Libyan MP, stopped by officials at Tripoli's city hall Wednesday when her handbag set off a security alarm, said a hand grenade inside was for her own defence.

Souad Soltan, a member of the General National Congress, had arrived at city hall for a meeting when she put her bag through the metal detector and set off the alarm, the city government said on its Facebook page.

"When the security officer asked her what was in the bag, she admitted there was a grenade that she carried for her own defence," a statement said.

Once the grenade was removed, she was allowed to carry on into the building and attend the meeting.

"After she left the meeting, she wanted the grenade back but the security officer refused."

The city council said it had issued the statement to deny rumours that Soltan had been arrested.

Libya has been plagued by growing lawlessness since the overthrow of the four-decade dictatorship of Moamer Kadhafi two years ago.

Last month, Prime Minister Ali Zeidan was himself briefly kidnapped by former rebel militia in the capital.

The violence continued on Wednesday, with a non-commissioned army officer killed in Kadhafi's hometown of Sirte and three people wounded in attacks elsewhere in the country, a security source said.

And an armoured car carrying $1.2 million (889,000 euros) to a branch of North African Bank in the southern town of Sebha was hijacked, state news agency LANA said.

The bank's manager has been taken in for questioning as a suspect because he had not arranged for sufficient security to accompany the shipment, the report added.