Gunfire rang out briefly on Wednesday near the presidency building in the capital, Nouakchott.
Taya was out of the country after attending the funeral of Saudi Arabia's King Fahd in Riyadh on Tuesday.
"We have heard that there has been a coup d'etat but we don't know who's involved. We don't know whether it is something that has succeeded or failed," Sid Ahmed Abeidna, the British honorary consul in Nouakchott, told Reuters.
The French embassy in Nouakchott said it was monitoring the situation in the former colony but declined to comment further.
Aljazeera has learned that the troops, led by Colonel Mohamed Walad Abd al-Aziz, also seized army headquarters.
A Reuters witness on the border with Senegal said border guards were preventing people from leaving the country.
Border guards reportedly prevented
people from leaving the country
Shops in the sand-blanketed city were closed and taxis were not stopping to pick up people trying to leave the town centre.
"I heard a burst of gunfire near the presidency. I saw scared people running away. Civil servants have all left their offices," a second Reuters witness in the capital said. He said
state radio had been off air since the early morning.
Dissident soldiers came close to toppling Taya in June 2003 during two days of street fighting in Nouakchott before loyalist forces regained control. The government says it foiled two more coup attempts in 2004.
"All the army is in the streets. It's blocking the roads to the presidency and the main routes through town," a civil servant who lives near the presidency building told Reuters.
Taya angered many for his
support of Israel and the US
Taya seized power in a 1984 coup.
He has angered many Arabs in the country, which straddles black and Arab Africa, by shifting support from former Iraqi President Saddam Hussein to Israel and Washington in the 1990s.
Mauritania, which hopes to start pumping oil early next year, is one of three Arab League member states that have established diplomatic ties with Israel.
It is also one of the most repressive countries in the region towards Islamist movements, analysts say.
Police have arrested scores of Islamic opposition leaders and activists since April, accusing them of colluding with the Algerian-based Salafist Group for Preaching and Combat (GSPC), a movement allied to al-Qaida.
In May, security forces searched mosques around the capital, seizing Quranic texts and arresting mosque officials.
Dissident troops came close to
toppling Taya in June 2003
The United States has been sending military experts to train soldiers in Mauritania and other countries in the region to combat militants thought to be operating in the Sahara.
US European Command, which overseas US military operations in 91 countries and territories in Europe and most of Africa, said it was monitoring the situation closely.
Analysts have warned that Mauritania's attempts to stifle opposition groups by denouncing them as terrorists risks backfiring by radicalising moderate Islamists.
Fifteen Mauritanian soldiers were killed in a dawn raid on a remote outpost near the Algerian border in June, an attack which the government blamed on the GSPC.