WASHINGTON (CNN) -- Cyber attacks on U.S. banks continued this week from suspected hackers believed to be supported by the Iranian government, according to U.S. officials.
Attacks on Capital One Financial Corp. and BB&T Corp. occurred on Tuesday and Wednesday. U.S. and banking officials described them as denial of service strikes preventing customers from accessing their information from banking websites.
There was little damage and no accounts were compromised, the officials said.
But the banks were still not able to fully stop the attacks even though it appeared they were pre-announced by at least one group.
American officials said earlier this week that attacks on U.S banks and oil companies in Saudi Arabia and Qatar over the past several months were believed to be carried out by surrogates supported by the Iranian government.
"There is a continuing stream of Iranian behavior ... these (attacks) have the hallmarks of Iranian cyber misbehavior," one U.S. official told Security Clearance.
Another official said the number of incidents targeting the banking industry have picked up in recent weeks.
Banks commented on the attacks.
"We did an experience an intermittent outage on BB&T.com and it was due to a denial of service event," said bank spokesman David White.
Tatiana Stead, a spokeswoman for Capital One, also said that bank experienced "some system delays on Tuesday due to a large volume of traffic going to the web site."
The chief executive of PNC Financial Services said Thursday in an interview on CNBC that it is believed Iran was behind the attack on his bank last month.
"We had the longest attack of all the banks," James Rohr said in interview excerpts posted on the CNBC website. He added that the hackers "just pummeled us."
A group called the Qassam Cyber Fighters claimed responsibility for the recent attacks with announcements online.
The group had also announced in recent days that it would continue the attacks this week in a posting on the same day Capital One was hit.
One of the U.S. officials said there is a belief within the intelligence community that Qassam Cyber Fighters is at least one of the surrogate groups backed by Iran conducting some of the cyber strikes.
Internet researchers are divided about how seriously to take the group's claims. It has launched attacks in the past, but those have been far less coordinated than the most recent ones.
The group has said the attacks are in retaliation for the same anti-Muslim film made in the United States that caused rioting and protests in several Muslim countries.
But the U.S. official said there is also a belief the cyber group has targeted banks in retaliation for western sanctions on Iran aimed at forcing Tehran to halt development of its nuclear program.
Defense Secretary Leon Panetta warned of increased cyber threats in a speech last week.
Though he never blamed Iran specifically, Panetta mentioned the previous banking and oil industry attacks that U.S. officials believe are linked to Iran.
The FBI is investigating the attacks and would not comment on any suspected connection to the Iranian government.