Large explosions were heard Thursday in the southern Yemeni city of Taiz, reported the broadcaster Al Jazeera, dpa reported
The report did not provide any details about possible casualties.
Taiz has been a focal point of anti-government protesters since political conflict erupted last February calling for Saleh to step down from 32 years of power.
Meanwhile, overnight clashes were also reported Thursday outside Yemen's southern city of Zinjibar, killing three soldiers and six militants, Lebanese television reported quoting official sources.
Militants linked to the terrorist organization al-Qaeda were believed to be attempting to regain control of Zinjibar, Yemen's largest city in the southern Abyan province, which is said to have come under their control since May.
Loud explosions were also heard across the province of Abyan.
Yemen has repeatedly said its forces were making gains against al-Qaeda militants. It said on Wednesday that it had pushed back militants from an area around 8 kilometres outside Zinjibar.
The country's political opponents, however, have accused Saleh of handing over the province to al-Qaeda militants in a bid to gain military and political support from the West in order to stay in power.
On Wednesday, Saleh accused the opposition of "corruption, lying, and deception" in a broadcast speech live from the Saudi' capital Riyadh where he is currently recovering from injuries sustained in an assault on his presidential palace June 3.
He described the opposition as "arms dealers" that are exploiting the youth protesters to overthrow his regime.