* Tanks drive down major street around midnight -witnesses
* Security appears normal in early morning
* No comment from officials on report
Sudan's security services thwarted a "sabotage attempt" led by opposition forces and arrested a number of civilian and military figures in connection with the incident early on Thursday, state-linked media reported.
Witnesses told Reuters they saw tanks and armoured vehicles moving down a major street in central Khartoum, the capital, around midnight. A Reuters reporter said security in the area appeared normal in the early morning.
Sudan, ruled by President Omar Hassan al-Bashir since he seized power in a 1989 coup, has avoided the massive political upheaval that has convulsed other Arab countries over the last two years.
But the secession of oil-producing South Sudan last year and an ensuing economic crisis emboldened some opposition activists to call for protests and, analysts say, exacerbated divisions in the government.
Small demonstrations against cuts in fuel subsidies and other austerity measures broke out across the country in June but petered out after a security crackdown and the start of the Muslim fasting month of Ramadan.
Sudan's security and intelligence agency "foiled a sabotage plot this morning aimed at bringing about security disturbances in the country led by figures from the opposition forces," the Sudanese Media Centre reported on Thursday.
Quoting a security source, the media centre said authorities had arrested "military and civilian figures" in connection with the plot. It did not identify them.
Officials could not immediately be reached for comment on the report. The Sudanese Media Centre earlier reported in a text message to mobile phones that the security and intelligence services had "frustrated a sabotage attempt".
Witnesses said they had seen military vehicles in a main street in central Khartoum during the night.
"We saw something unusual in Khartoum before midnight yesterday. Four armoured vehicles and two tanks on Abeid Khatim Street heading in the direction of downtown," one witness said, asking not to be named.
Security at the defence ministry, intelligence headquarters and other buildings associated with military and security authorities appeared normal early in the morning, a Reuters witness said.
Sudan has been plagued by political conflicts and crises for most of its history since independence from Britain in 1956.
Decades of civil war between the north and south culminated with South Sudan's independence in July last year under a 2005 peace deal.
Tensions have remained high since then. The two countries accused one another of incursions in disputed border zones on Wednesday, a setback to recent security and border deals.