* Jordan's ambassador was kidnapped on Tuesday
* Libyan government struggling to contain violence
* Kidnapped Tunisian was advisor at embassy (Adds comments from Libyan foreign minister, details of kidnapping, Tunisia issuing travel warning.)
By Feras Bosalum and Tarek Amara
TRIPOLI/TUNIS, April 17 (Reuters) - A Tunisian diplomat was kidnapped on Thursday in the Libyan capital Tripoli, Libya's foreign ministry said, two days after gunmen seized Jordan's ambassador.
Kidnappings have become commonplace in the oil producer, with foreign officials often the targets.
The weak interim government has been unable to disarm former rebels and Islamist militants who fought to depose leader Muammar Gaddafi in 2011 and who have formed increasingly powerful and violent militias.
Libyan foreign minister Mohamed Abdelaziz told Reuters by phone unknown people had seized the diplomat and brought him to an unknown location. "This is correct," he said, when asked whether the diplomat had been kidnapped.
The Tunisian diplomat called Aroussi Gantassi had not gone to the embassy on Thursday, a foreign ministry spokesman told state news agency LANA.
Neither his car nor his house had been damaged. "Therefore we assume that the advisor Aroussi Gantassi is in good health," the spokesman said, according to the agency.
An official in Tunisia's foreign ministry said: "We cannot confirm that he has been kidnapped but we have been unable to contact him." He said the missing diplomat works as an adviser at the Tunisian embassy in Tripoli.
"Tunisia is worried about Tunisian diplomats getting targeted in Libya," Tunisia's foreign ministry said in a statement. "We ask Tunisians for caution in Libya and to postpone travel to Libya."
On Tuesday, gunmen kidnapped Jordan's ambassador to Libya and demanded an Islamist militant be released from a Jordanian jail in exchange for the diplomat's freedom.
Masked men shot and wounded the driver of Ambassador Fawaz al-Itan's car as they snatched the diplomat from a street in the capital Tripoli.
Last week, Libya's interim prime minister resigned after just one month into the job, saying gunmen had tried to attack his family.
Local officials, policemen and army personnel are also targeted and there have been some random acts of violence against ordinary foreigners.
In December, an American teacher was shot dead in Benghazi and in January, a British man and a woman from New Zealand were shot execution-style on a beach in western Libya.
One month later, seven Egyptian Christians were found dead, having been killed in a similar manner.
Tribal groups, militias and even local citizens resort to road blockades as a negotiating tactic. Some have even resorted to shutting down the OPEC member's vital oil facilities. (Reporting by Feras Bosalum and Tarek Amara; Writing by Ulf Laessing; Editing by Raissa Kasolowsky and Andrew Hay)